[Backport maintenance/3.3.x] Fix source root not recognized

[github-actions]

Backport be53085 from #10036.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.80%. Comparing base (ec4ca64) to head (bc37374).
Report is 1 commits behind head on maintenance/3.3.x.

Additional details and impacted files

@@                Coverage Diff                 @@
##           maintenance/3.3.x   #10083   +/-   ##
==================================================
  Coverage              95.80%   95.80%           
==================================================
  Files                    174      174           
  Lines                  18940    18940           
==================================================
  Hits                   18146    18146           
  Misses                   794      794           

Files with missing lines	Coverage Δ
pylint/lint/expand_modules.py	95.29% <100.00%> (ø)