Fix broken links to use cases (#12777)

This PR replaces broken links to end to end usecases
([/docs/use_cases](https://python.langchain.com/docs/use_cases)) with a
non-broken version
([/docs/use_cases/qa_structured/sql](https://python.langchain.com/docs/use_cases/qa_structured/sql)),
consistently with the "Use cases" navigation button at the top of the
page.

---------

Co-authored-by: Matvey Arye <mat@timescale.com>
Co-authored-by: Erick Friis <erick@langchain.dev>

docs/docs/additional_resources/tutorials.mdx

@@ -1,6 +1,6 @@
 # Tutorials
 
-Below are links to tutorials and courses on LangChain. For written guides on common use cases for LangChain, check out the [use cases guides](/docs/use_cases).
+Below are links to tutorials and courses on LangChain. For written guides on common use cases for LangChain, check out the [use cases guides](/docs/use_cases/qa_structured/sql).
 
 ⛓ icon marks a new addition [last update 2023-09-21]