docs: Correct WebBaseLoader URL: docs: python.langchain.com/docs/get_started/quickstartQuickstart (#17981)
**Description:**
The URL of the data to index, specified to `WebBaseLoader` to import is
incorrect, causing the `langsmith_search` retriever to return a `404:
NOT_FOUND`.
Incorrect URL: https://docs.smith.langchain.com/overview
Correct URL: https://docs.smith.langchain.com
**Issue:**
This commit corrects the URL and prevents the LangServe Playground from
returning an error from its inability to use the retriever when
inquiring, "how can langsmith help with testing?".
**Dependencies:**
None.
**Twitter Handle:**
@ryanmeinzer