Issue:
Bug: [FIX] Remove ToSchema from RefundAggregateResponse and exclude it from OpenAPI documentation



### Feature Description

The RefundAggregateResponse type used by the [/refunds/aggregate](https://github.com/juspay/hyperswitch/blob/37925626e6446900f1d16e0e5f184ee472d4be3e/crates/router/src/routes/app.rs#L1004) API is currently annotated with ToSchema, which generates OpenAPI schema documentation for it. However, since this API is internal and should not be exposed to external users, the schema should not be generated or included in the OpenAPI documentation.

Current Behavior:
- The `RefundAggregateResponse` struct is annotated with ToSchema, which automatically generates OpenAPI documentation.
- This results in the exposure of internal API details that should remain hidden from external consumers.

Expected Behavior:
- Remove the `ToSchema` derive macro from the RefundAggregateResponse struct.
- Ensure that this struct and its associated API are excluded from OpenAPI documentation generation.

### Possible Implementation


The Api [refunds/aggregate](https://github.com/juspay/hyperswitch/blob/37925626e6446900f1d16e0e5f184ee472d4be3e/crates/router/src/core/refunds.rs#L1098) returns `RefundAggregateResponse`
The following code should be modified to remove ToSchema and update the OpenAPI documentation accordingly:
```
#[derive(Clone, Debug, serde::Serialize, ToSchema)] 
pub struct RefundAggregateResponse {
    /// The list of refund status with their count
    pub status_with_count: HashMap<enums::RefundStatus, i64>,
}
```

Tasks:
- Remove the ToSchema derive macro from the RefundAggregateResponse struct.
- Remove any references to RefundAggregateResponse from openapi.rs to ensure it is not documented.
- Test to verify that this type is no longer included in the OpenAPI schema.

Additional Context:
Since the `/refunds/aggregate` API is for internal use only, removing the OpenAPI schema ensures that this internal API remains undocumented for merchants.

### Have you spent some time checking if this feature request has been raised before?

- [X] I checked and didn't find a similar issue

### Submission Process:
- Ask the maintainers for assignment of the issue, you can request for assignment by commenting on the issue itself.
- Once assigned, submit a pull request (PR).
- Maintainers will review and provide feedback, if any. 
- Maintainers can unassign issues due to inactivity, [read more here](https://github.com/juspay/hyperswitch/wiki/Hacktoberfest-Contribution-Rules).

Refer [here](https://github.com/juspay/hyperswitch/blob/main/docs/TERMS_OF_CONTEST.md) for Terms and conditions for the contest.

Pull request description:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [x] Bugfix
- [ ] New feature
- [ ] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
<!-- Describe your changes in detail -->
Removed all the openapi references to `RefundAggregateResponse`.

1. Removed `ToSchema` trait for `RefundAggregateResponse`.
2. Removed references from `openapi` and `openapi_v2` to `RefundAggregateResponse`.
3. Generated new `openapi_spec` file based on the above changes.


### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables

<!--
Provide links to the files with corresponding changes.

Following are the paths where you can find config files:
1. `config`
2. `crates/router/src/configs`
3. `loadtest/config`
-->

## Motivation and Context
<!--
Why is this change required? What problem does it solve?
If it fixes an open issue, please link to the issue here.

If you don't have an issue, we'd recommend starting with one first so the PR
can focus on the implementation (unless it is an obvious bug or documentation fix
that will have little conversation).
-->
#5990

## How did you test it?
<!--
Did you write an integration/unit/API test to verify the code changes?
Or did you test this change manually (provide relevant screenshots)?
-->
Tested manually.
The references of `RefundAggregateResponse` is removed in openapi generated  json file after the modification.
<img width="871" alt="image" src="https://github.com/user-attachments/assets/70f23a10-37e9-420e-8031-f41e6b5f11da">

<img width="1015" alt="image" src="https://github.com/user-attachments/assets/614b9c86-2735-445c-8aa0-d54248f944a5">


## Checklist
<!-- Put an `x` in the boxes that apply -->

- [x] I formatted the code `cargo +nightly fmt --all`
- [x] I addressed lints thrown by `cargo clippy`
- [x] I reviewed the submitted code
- [ ] I added unit tests for my changes where possible


Testing:

Tested manually.
The references of `RefundAggregateResponse` is removed in openapi generated  json file after the modification.
<img width="871" alt="image" src="https://github.com/user-attachments/assets/70f23a10-37e9-420e-8031-f41e6b5f11da">

<img width="1015" alt="image" src="https://github.com/user-attachments/assets/614b9c86-2735-445c-8aa0-d54248f944a5">

Patch:
diff --git a/api-reference-v2/openapi_spec.json b/api-reference-v2/openapi_spec.json
index 72afa1dc3da..63c01329dfe 100644
--- a/api-reference-v2/openapi_spec.json
+++ b/api-reference-v2/openapi_spec.json
@@ -18158,22 +18158,6 @@
           }
         }
       },
-      "RefundAggregateResponse": {
-        "type": "object",
-        "required": [
-          "status_with_count"
-        ],
-        "properties": {
-          "status_with_count": {
-            "type": "object",
-            "description": "The list of refund status with their count",
-            "additionalProperties": {
-              "type": "integer",
-              "format": "int64"
-            }
-          }
-        }
-      },
       "RefundErrorDetails": {
         "type": "object",
         "required": [
diff --git a/crates/api_models/src/refunds.rs b/crates/api_models/src/refunds.rs
index f42eb8095b4..ac5e5cb4618 100644
--- a/crates/api_models/src/refunds.rs
+++ b/crates/api_models/src/refunds.rs
@@ -346,7 +346,7 @@ pub struct RefundListFilters {
     pub refund_status: Vec<enums::RefundStatus>,
 }
 
-#[derive(Clone, Debug, serde::Serialize, ToSchema)]
+#[derive(Clone, Debug, serde::Serialize)]
 pub struct RefundAggregateResponse {
     /// The list of refund status with their count
     pub status_with_count: HashMap<enums::RefundStatus, i64>,
diff --git a/crates/openapi/src/openapi.rs b/crates/openapi/src/openapi.rs
index 28a7f44c7a8..754ec433b77 100644
--- a/crates/openapi/src/openapi.rs
+++ b/crates/openapi/src/openapi.rs
@@ -492,7 +492,6 @@ Never share your secret api keys. Keep them guarded and secure.
         api_models::payment_methods::PaymentMethodCollectLinkResponse,
         api_models::refunds::RefundListRequest,
         api_models::refunds::RefundListResponse,
-        api_models::refunds::RefundAggregateResponse,
         api_models::payments::AmountFilter,
         api_models::mandates::MandateRevokedResponse,
         api_models::mandates::MandateResponse,
diff --git a/crates/openapi/src/openapi_v2.rs b/crates/openapi/src/openapi_v2.rs
index 7c961b2b2b2..84f320778fe 100644
--- a/crates/openapi/src/openapi_v2.rs
+++ b/crates/openapi/src/openapi_v2.rs
@@ -432,7 +432,6 @@ Never share your secret api keys. Keep them guarded and secure.
         api_models::payment_methods::PaymentMethodCollectLinkResponse,
         api_models::refunds::RefundListRequest,
         api_models::refunds::RefundListResponse,
-        api_models::refunds::RefundAggregateResponse,
         api_models::payments::AmountFilter,
         api_models::mandates::MandateRevokedResponse,
         api_models::mandates::MandateResponse,