Repository: langchain
Issue: Replicate LLM - api token passed in constructor is not used to access the service.
Labels: 🤖:bug

### Checked other resources

- [X] I added a very descriptive title to this issue.
- [X] I searched the LangChain documentation with the integrated search.
- [X] I used the GitHub search to find a similar question and didn't find it.
- [X] I am sure that this is a bug in LangChain rather than my code.
- [X] The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).

### Example Code

```
from langchain_community.llms.replicate import Replicate
import os

TEST_MODEL_HELLO = (
    "replicate/hello-world:"
    + "5c7d5dc6dd8bf75c1acaa8565735e7986bc5b66206b55cca93cb72c9bf15ccaa"
)
# Grab the api token from the environment variable.
api_token = os.getenv("REPLICATE_API_TOKEN")

# Reset the environment variable to ensure it's not available.
os.environ["REPLICATE_API_TOKEN"] = "yo"

# Pass the api token into the model.
llm = Replicate(model=TEST_MODEL_HELLO, replicate_api_token=api_token)
output = llm.invoke("What is a duck?")
```

### Error Message and Stack Trace (if applicable)

```
resp = <Response [401 Unauthorized]>

    def _raise_for_status(resp: httpx.Response) -> None:
        if 400 <= resp.status_code < 600:
>           raise ReplicateError.from_response(resp)
E           replicate.exceptions.ReplicateError: ReplicateError Details:
E           title: Unauthenticated
E           status: 401
E           detail: You did not pass a valid authentication token

../../../../../.venv/lib/python3.10/site-packages/replicate/client.py:393: ReplicateError
```

### Description

I am passing an api token explicitly into the Replicate LLM model client constructor, without setting the token as an environment variable. I would like that token to be used for all access to the Replicate service.

When making requests to the service for things like the model version, instead of using this api key, the Replicate model uses the default Client, which gets its token from the env var.

Please ensure the api token that is used to construct the Replicate model client is used for all service access.

### System Info

% python -m langchain_core.sys_info
```
System Information
------------------
> OS:  Darwin
> OS Version:  Darwin Kernel Version 23.6.0: Mon Jul 29 21:14:46 PDT 2024; root:xnu-10063.141.2~1/RELEASE_ARM64_T6031
> Python Version:  3.10.15 (main, Sep 11 2024, 20:50:01) [Clang 12.0.0 (clang-1200.0.32.29)]

Package Information
-------------------
> langchain_core: 0.3.15
> langchain: 0.3.7
> langchain_community: 0.3.5
> langsmith: 0.1.139
> langchain_text_splitters: 0.3.2

Optional packages not installed
-------------------------------
> langgraph
> langserve

Other Dependencies
------------------
> aiohttp: 3.10.10
> async-timeout: 4.0.3
> dataclasses-json: 0.6.7
> httpx: 0.27.2
> httpx-sse: 0.4.0
> jsonpatch: 1.33
> numpy: 1.26.4
> orjson: 3.10.11
> packaging: 24.1
> pydantic: 2.9.2
> pydantic-settings: 2.6.1
> PyYAML: 6.0.2
> requests: 2.32.3
> requests-toolbelt: 1.0.0
> SQLAlchemy: 2.0.35
> tenacity: 9.0.0
> typing-extensions: 4.12.2
```