ci: Ensure release-plz always pushes as @hugrbot

[aborgna-q]

This should solve the issue where CI checks wouldn't run in release PRs unless a human triggered an update.

See https://github.com/MarcoIeni/release-plz/blob/main/website/docs/github/token.md#use-a-personal-access-token

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.57%. Comparing base (ee39f66) to head (1493948).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #147   +/-   ##
=======================================
  Coverage   80.57%   80.57%           
=======================================
  Files          22       22           
  Lines        5173     5173           
  Branches     5173     5173           
=======================================
  Hits         4168     4168           
  Misses        932      932           
  Partials       73       73           

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