linter fixes

[vivus-ignis]

What this PR does / why we need it:

Which issue(s) this PR fixes:
Fixes (partially) #165

Special notes for your reviewer:

Fixes for linters checks only:

• fixed formatting to please black
• fixed imports style to please isort
• removed unused imports
• disabled unnecessary pyright checks for the new code (github module & its tests)

[codecov]

Codecov Report

❌ Patch coverage is 94.44444% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.17%. Comparing base (c197e25) to head (00c8cce).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
src/gardenlinux/github/release_notes/helpers.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #233      +/-   ##
==========================================
- Coverage   90.24%   90.17%   -0.07%     
==========================================
  Files          42       42              
  Lines        2009     1995      -14     
==========================================
- Hits         1813     1799      -14     
  Misses        196      196              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[NotTheEvilOne]

LGTM