Better handling of git actor

[blink1073]

• Use the current actor set set the git user
• Ensure the authenticated user has admin permissions to run the actions

Fixes #423

[codecov-commenter]

Codecov Report

Base: 81.59% // Head: 81.30% // Decreases project coverage by -0.28% ⚠️

Coverage data is based on head (536a0cf) compared to base (593f261).
Patch coverage: 16.66% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #424      +/-   ##
==========================================
- Coverage   81.59%   81.30%   -0.29%     
==========================================
  Files          20       20              
  Lines        2776     2782       +6     
  Branches      358      360       +2     
==========================================
- Hits         2265     2262       -3     
- Misses        385      392       +7     
- Partials      126      128       +2     

Impacted Files	Coverage Δ
jupyter_releaser/tests/test_cli.py	98.85% <ø> (ø)
jupyter_releaser/util.py	71.12% <0.00%> (-0.78%)	⬇️
jupyter_releaser/lib.py	77.71% <28.57%> (-1.15%)	⬇️

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[blink1073]

Validated in https://github.com/blink1073/test-python-project/actions/runs/3198498454/jobs/5223089910