chore(rails): 8.1 in test setup

[solnic]

#skip-changelog

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.25%. Comparing base (d643fcd) to head (2bdf4ff).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2764   +/-   ##
=======================================
  Coverage   97.25%   97.25%           
=======================================
  Files         130      130           
  Lines        5240     5240           
=======================================
  Hits         5096     5096           
  Misses        144      144           

Components	Coverage Δ
sentry-ruby	97.54% <ø> (ø)
sentry-rails	96.78% <ø> (ø)
sentry-sidekiq	95.05% <ø> (ø)
sentry-resque	94.44% <ø> (ø)
sentry-delayed_job	94.68% <ø> (ø)
sentry-opentelemetry	99.31% <ø> (ø)

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