Remove JAX from pip install in Job Search II lecture

The JAX library is already included in the base environment and doesn't need
to be explicitly installed, which was causing build failures.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: jstac

lectures/mccall_model_with_separation.md

@@ -34,7 +34,7 @@ In addition to what's in Anaconda, this lecture will need the following librarie
 ```{code-cell} ipython3
 :tags: [hide-output]
 
-!pip install quantecon jax
+!pip install quantecon
 ```
 
 ## Overview