combinatorial_designs package is superfluous

[AndreasEnge]

Steps To Reproduce

No response

Expected Behavior

Only actually used packages are referenced in the git repository.

Actual Behavior

Since commit f83fabf , the content (only one file) of the combinatorial_designs package has been copied into a Python file in the Sage repository (currently, src/sage/combinat/designs/MOLS_handbook_data.py).
But the subdirectory build/pkgs/combinatorial_designs is still there.

Additional Information

No response

Environment

all systems

Checklist

• I have searched the existing issues for a bug report that matches the one I want to file, without success.
• I have read the documentation and troubleshoot guide