fix mypy extra unit tests, pin pandas-stubs for dev env

[cosmicBboy]

Signed-off-by: Niels Bantilan niels.bantilan@gmail.com

This PR:

• updates the pandera[mypy] extras tests
• pins pandas-stubs in the dev requirements. Since this package is still under development and changes often, this will cause mypy errors in the pandera codebase, which will break CI in PRs that don't have anything to do with mypy.
• update the pre-commit hook to apply to source directories instead of individual files.

[codecov]

Codecov Report

Base: 97.68% // Head: 97.60% // Decreases project coverage by -0.07% ⚠️

Coverage data is based on head (e4d6918) compared to base (5aa7795).
Patch coverage: 87.50% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1056      +/-   ##
==========================================
- Coverage   97.68%   97.60%   -0.08%     
==========================================
  Files          41       42       +1     
  Lines        4268     4303      +35     
==========================================
+ Hits         4169     4200      +31     
- Misses         99      103       +4     

Impacted Files	Coverage Δ
pandera/schemas.py	99.43% <ø> (ø)
pandera/engines/pandas_engine.py	97.50% <66.66%> (ø)
pandera/checks.py	98.57% <100.00%> (ø)
pandera/decorators.py	99.51% <100.00%> (+<0.01%)	⬆️
pandera/strategies.py	98.26% <100.00%> (ø)
pandera/__init__.py	87.87% <0.00%> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.