docs[patch]: Update CONTRIBUTING.md doc (#13965)

- **Description:** The new demo notebook should be placed in
[docs/docs/modules](https://github.com/langchain-ai/langchain/tree/master/docs/docs/modules)
  - **Twitter handle:**  lin_bob57617

---------

Co-authored-by: Bagatur <baskaryan@gmail.com>

.github/CONTRIBUTING.md

@@ -23,7 +23,7 @@ It's essential that we maintain great documentation and testing. If you:
   - Update any affected example notebooks and documentation. These live in `docs`.
   - Update unit and integration tests when relevant.
 - Add a feature
-  - Add a demo notebook in `docs/modules`.
+  - Add a demo notebook in `docs/docs/`.
   - Add unit and integration tests.
 
 We are a small, progress-oriented team. If there's something you'd like to add or change, opening a pull request is the