community: Fix a validation error for MoonshotChat (#27801)

- **Description:** Change `MoonshotCommon.client` type from
`_MoonshotClient` to `Any`.
- **Issue:** Fix the issue #27058
- **Dependencies:** No
- **Twitter handle:** TaoWang2218

In PR #17100, the implementation for Moonshot was added, which defined
two classes:

- `MoonshotChat(MoonshotCommon, ChatOpenAI)` in
`langchain_community.chat_models.moonshot`;
- Here, `validate_environment()` assigns **client** as
`openai.OpenAI().chat.completions`
- Note that **client** here is actually a member variable defined in
`ChatOpenAI`;
- `MoonshotCommon` in `langchain_community.llms.moonshot`;
- And here, `validate_environment()` assigns **_client** as
`_MoonshotClient`;
- Note that this is the underscored **_client**, which is defined within
`MoonshotCommon` itself;

At this time, there was no conflict between the two, one being `client`
and the other `_client`.

However, in PR #25878 which fixed #24390, `_client` in `MoonshotCommon`
was changed to `client`. Since then, a conflict in the definition of
`client` has arisen between `MoonshotCommon` and `MoonshotChat`, which
caused `pydantic` validation error.

To fix this issue, the type of `client` in `MoonshotCommon` should be
changed to `Any`.

Signed-off-by: Tao Wang <twang2218@gmail.com>

libs/community/langchain_community/llms/moonshot.py

@@ -39,7 +39,7 @@ class _MoonshotClient(BaseModel):
 class MoonshotCommon(BaseModel):
     """Common parameters for Moonshot LLMs."""
 
-    client: _MoonshotClient
+    client: Any
     base_url: str = MOONSHOT_SERVICE_URL_BASE
     moonshot_api_key: Optional[SecretStr] = Field(default=None, alias="api_key")
     """Moonshot API key. Get it here: https://platform.moonshot.cn/console/api-keys"""