docs: docstrings langchain_community update (#14889)

Addded missed docstrings. Fixed inconsistency in docstrings.

**Note** CC @efriis 
There were PR errors on
`langchain_experimental/prompt_injection_identifier/hugging_face_identifier.py`
But, I didn't touch this file in this PR! Can it be some cache problems?
I fixed this error.

libs/community/langchain_community/tools/arxiv/tool.py

@@ -10,6 +10,8 @@ from langchain_community.utilities.arxiv import ArxivAPIWrapper
 
 
 class ArxivInput(BaseModel):
+    """Input for the Arxiv tool."""
+
     query: str = Field(description="search query to look up")