Fix temp git clones clutter issue.

[BoubQC]

Use filesystem.safe_delete_folder instead of shutil.rmtree since the later doesn't delete read-only files.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.82%. Comparing base (4f3880b) to head (e74fe51).
⚠️ Report is 180 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (4f3880b) and HEAD (e74fe51). Click for more details.

HEAD has 11 uploads less than BASE

Flag	BASE (4f3880b)	HEAD (e74fe51)
	19	8

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #845      +/-   ##
==========================================
- Coverage   79.38%   72.82%   -6.56%     
==========================================
  Files         177      177              
  Lines       19302    19302              
==========================================
- Hits        15322    14056    -1266     
- Misses       3980     5246    +1266     

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[staceyoue]

LGTM!