Enable get-attr-with-constant (B009)

[tqa236]

The original reasoning to disable this rule is because getattr is needed to side step mypy, but mypy doesn't complain about the fix anymore.

• closes #xxxx (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.

[mroeschke]

Thanks @tqa236