[Do not merge] chore(pyproject.toml): update test packages

[nkemnitz]

• remove flake8 (unused)
• remove duplicate coverage generation (pytest already configured to output coverage)

[codecov]

Codecov Report

❌ Patch coverage is 97.36842% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 99.95%. Comparing base (2d68995) to head (3f4c1ca).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
zetta_utils/__init__.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1098      +/-   ##
==========================================
- Coverage   99.97%   99.95%   -0.03%     
==========================================
  Files         179      179              
  Lines        8694     8680      -14     
==========================================
- Hits         8692     8676      -16     
- Misses          2        4       +2     

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