Expand mypy CI checks to three more files

[correctmost]

Type of Changes

	Type
✓	🔨 Refactoring

Description

This PR adds a few more files to the passing list to prevent new warnings from slipping in.

[Pierre-Sassoulas]

Great !

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.24%. Comparing base (2d26795) to head (d7d06d6).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2636   +/-   ##
=======================================
  Coverage   93.24%   93.24%           
=======================================
  Files          93       93           
  Lines       11060    11061    +1     
=======================================
+ Hits        10313    10314    +1     
  Misses        747      747           

Flag	Coverage Δ
linux	93.13% <100.00%> (+<0.01%)	⬆️
pypy	93.24% <100.00%> (+<0.01%)	⬆️
windows	93.24% <100.00%> (+<0.01%)	⬆️

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Files with missing lines	Coverage Δ
astroid/brain/brain_mechanize.py	100.00% <100.00%> (ø)
astroid/context.py	97.43% <ø> (ø)
astroid/modutils.py	89.47% <100.00%> (ø)