update offsets.pyx to fix #60647

[kangqiwang]

• [x ] closes BUG: CustomBusinessDay not respecting calendar #60647 (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

[kangqiwang]

Sorry for not adding a test case for this. I'll set it up once I get home and can work on my PC—my current laptop is too slow to handle the full testing environment.

[kangqiwang]

Also, I noticed the unit tests failed. Again, I will fix them once I get home.

[a-holm]

Thanks for working on this fix for #60647!

This change successfully removes the code path containing the specific line (holidays = holidays + calendar.holidays().tolist()) identified in the issue and the comments.

However, there are a few points that probably deserve some attention:

Removed Functionality: This fix works by removing the if-else block. Was the functionality within that block (handling a non-numpy calendar object passed with holidays) intended or ever valid? Removing it is a potentially breaking change that should ideally be documented.

Exception Type: Raising ApplyTypeError here is a bit unusual, as it's typically for arithmetic operations returning NotImplemented. Would a ValueError or TypeError be more appropriate to signal invalid arguments during the setup phase?