chore: remove out-of-date renovate config

[m1sk9]

Cherry-picked from https://github.com/pulsate-dev/pulsate.dev/commit/3fbbeb65f2c9079bb93514b8b79ba9547270d49d, https://github.com/pulsate-dev/pulsate.dev/commit/afb7b6a97c3c78a5c446bcb53fe1186558dcd854

What does this PR do?

Removed outdated renovate settings and fixed an auto-assign workflow that prevented renovate from being assigned.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.56%. Comparing base (4be7ae5) to head (203410d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #409   +/-   ##
=======================================
  Coverage   66.56%   66.56%           
=======================================
  Files          52       52           
  Lines        5348     5348           
  Branches      417      417           
=======================================
  Hits         3560     3560           
  Misses       1788     1788           

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