feat(deps): update deprecated go client

[LucasMrqes]

This updates the deprecated gitlab package go-gitlab in favor of client-go.
Also ran go mod tidy to clean deps.

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 50.05%. Comparing base (c1812f6) to head (55aeef2).
Report is 1 commits behind head on main.

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Additional details and impacted files

@@           Coverage Diff           @@
##             main     #452   +/-   ##
=======================================
  Coverage   50.05%   50.05%           
=======================================
  Files          72       72           
  Lines        4805     4805           
=======================================
  Hits         2405     2405           
  Misses       2197     2197           
  Partials      203      203           

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