docs: Update import in wikipedia tool documentation (#21565)
Updates docs so the example doesn't lead to a warning:
```
LangChainDeprecationWarning: Importing tools from langchain is deprecated. Importing from langchain will no longer be supported as of langchain==0.2.0. Please import from langchain-community instead:
`from langchain_community.tools import WikipediaQueryRun`.
To install langchain-community run `pip install -U langchain-community`.
```
