[Backport maintenance/3.3.x] fix "skipped files" count calculation

[github-actions]

Backport d94194b from #10141.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.81%. Comparing base (c28580b) to head (6c30fca).
Report is 1 commits behind head on maintenance/3.3.x.

Additional details and impacted files

@@                Coverage Diff                 @@
##           maintenance/3.3.x   #10175   +/-   ##
==================================================
  Coverage              95.81%   95.81%           
==================================================
  Files                    174      174           
  Lines                  18954    18961    +7     
==================================================
+ Hits                   18160    18167    +7     
  Misses                   794      794           

Files with missing lines	Coverage Δ
pylint/lint/expand_modules.py	95.40% <100.00%> (+0.10%)	⬆️
pylint/lint/pylinter.py	96.66% <100.00%> (+0.01%)	⬆️
pylint/typing.py	100.00% <100.00%> (ø)
pylint/utils/linterstats.py	98.80% <100.00%> (+0.01%)	⬆️