Doc: Fix copy parameter type in astype docstring Fixes #63144

[blu3-bird]

Fixes #63144

Summary

Corrects the type annotation and default value for the copy parameter in the astype() docstring to match the actual function signature.

Changes

• Updated copy parameter from bool, default False to bool or lib.NoDefault, default lib.no_default
• Location: pandas/core/generic.py, line ~6508

Before:
copy : bool, default False

After:
copy : bool or lib.NoDefault, default lib.no_default

[rhshadrach]

Thanks for the PR but I'm negative on this change. The use of lib.no_default is just to enable the deprecation. When a user does not specify copy, they still get False behavior.