chore(deps): bump to fixed django-celery-beat

[jennifer-richards]

django-celery-beat 2.8.1 is out with the fix for the time zone issue. We could fall back to >= 2.3.0 because they've yanked the broken release, but I don't see any reason to allow the old versions.

Should be safe to install this immediately since they're all currently in UTC. We can later test that schedules in non-UTC time zones do in fact run, then convert our schedules back to America/Los_Angeles (if we want to do so).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.79%. Comparing base (279cbee) to head (67b0fcd).
Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8896   +/-   ##
=======================================
  Coverage   88.79%   88.79%           
=======================================
  Files         314      314           
  Lines       41402    41402           
=======================================
  Hits        36764    36764           
  Misses       4638     4638           

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[rjsparks]

Lets take this opportunity to make the move to doing things in UTC stick.