Repository: langchain
Issue: ChatAnthropicVertex not respecting `api_endpoint` or `base_url`
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

```py
import logging

logging.basicConfig(
    level=logging.DEBUG,
    format="%(asctime)s.%(msecs)03d %(levelname)s %(module)s - %(funcName)s: %(message)s",
    datefmt="%Y-%m-%d %H:%M:%S",
    force=True,
)

from langchain_google_vertexai.model_garden import ChatAnthropicVertex
chat = ChatAnthropicVertex(
        model_name="claude-3-5-sonnet@20240620",
        project="thecoo-data-platform",
        base_url='https://example.com'
    )

chat.invoke("hello")
```

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

```
2024-10-31 13:30:21.065 DEBUG _trace - trace: receive_response_headers.started request=<Request [b'POST']>
2024-10-31 13:30:21.996 DEBUG _trace - trace: receive_response_headers.complete return_value=(b'HTTP/1.1', 400, b'Bad Request', [(b'Vary', b'Origin'), (b'Vary', b'X-Origin'), (b'Vary', b'Referer'), (b'Content-Type', b'application/json; charset=UTF-8'), (b'Content-Encoding', b'gzip'), (b'Date', b'Thu, 31 Oct 2024 04:30:21 GMT'), (b'Server', b'scaffolding on HTTPServer2'), (b'Cache-Control', b'private'), (b'X-XSS-Protection', b'0'), (b'X-Frame-Options', b'SAMEORIGIN'), (b'X-Content-Type-Options', b'nosniff'), (b'Alt-Svc', b'h3=":443"; ma=2592000,h3-29=":443"; ma=2592000'), (b'Transfer-Encoding', b'chunked')])
2024-10-31 13:30:21.998 INFO _client - _send_single_request: HTTP Request: POST https://us-central1-aiplatform.googleapis.com/v1/projects/project_id/locations/us-central1/publishers/anthropic/models/claude-3-5-sonnet@20240620:rawPredict "HTTP/1.1 400 Bad Request"
2024-10-31 13:30:21.999 DEBUG _trace - trace: receive_response_body.started request=<Request [b'POST']>
2024-10-31 13:30:22.001 DEBUG _trace - trace: receive_response_body.complete
2024-10-31 13:30:22.002 DEBUG _trace - trace: response_closed.started
2024-10-31 13:30:22.003 DEBUG _trace - trace: response_closed.complete

........

httpx.HTTPStatusError: Client error '400 Bad Request' for url 'https://us-central1-aiplatform.googleapis.com/v1/projects/project_id/locations/us-central1/publishers/anthropic/models/claude-3-5-sonnet@20240620:rawPredict'
For more information check: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/400
```


### Description

[the doc of ChatAnthropicVertex](https://api.python.langchain.com/en/latest/google_vertexai/model_garden/langchain_google_vertexai.model_garden.ChatAnthropicVertex.html#langchain_google_vertexai.model_garden.ChatAnthropicVertex) mentions the `api_endpoint` or `base_url` parameter, but they are not affecting (I tried both).

As can be seen from the logs, http request went to `https://us-central1-aiplatform.googleapis.com`

### System Info

```
System Information
------------------
> OS:  Darwin
> OS Version:  Darwin Kernel Version 23.6.0: Mon Jul 29 21:13:00 PDT 2024; root:xnu-10063.141.2~1/RELEASE_X86_64
> Python Version:  3.11.0 | packaged by conda-forge | (main, Jan 15 2023, 05:44:48) [Clang 14.0.6 ]

Package Information
-------------------
> langchain_core: 0.3.14
> langchain: 0.3.1
> langchain_community: 0.3.1
> langsmith: 0.1.129
> langchain_anthropic: 0.2.1
> langchain_elasticsearch: 0.3.0
> langchain_google_vertexai: 2.0.6
> langchain_groq: 0.2.0
> langchain_openai: 0.2.1
> langchain_text_splitters: 0.3.0
> langgraph: 0.2.32

Optional packages not installed
-------------------------------
> langserve

Other Dependencies
------------------
> aiohttp: 3.10.8
> anthropic: 0.34.2
> anthropic[vertexai]: Installed. No version info available.
> async-timeout: 4.0.3
> dataclasses-json: 0.6.7
> defusedxml: 0.7.1
> elasticsearch[vectorstore-mmr]: Installed. No version info available.
> google-cloud-aiplatform: 1.71.0
> google-cloud-storage: 2.18.2
> groq: 0.11.0
> httpx: 0.27.2
> httpx-sse: 0.4.0
> jsonpatch: 1.33
> langchain-mistralai: Installed. No version info available.
> langgraph-checkpoint: 2.0.0
> numpy: 1.26.4
> openai: 1.53.0
> orjson: 3.10.7
> packaging: 24.1
> pydantic: 2.9.2
> pydantic-settings: 2.5.2
> PyYAML: 6.0.2
> requests: 2.32.3
> SQLAlchemy: 2.0.35
> tenacity: 8.5.0
> tiktoken: 0.7.0
> typing-extensions: 4.12.2
```