Revert 1070 (Celery tasks.py)

[n2ygk]

Fixes #1114
Fixes #1123

Description of the Change

#1070 was apparently not tested (and was not supplied with a test case). It could never have worked and also has since been flagged as conflicting with Huey's auto-discovery which also uses tasks.py.

A future PR might come which will document how to configure a Celery clear_tokens task.

Checklist

• PR only contains one change (considered splitting up PR)
• unit-test added
• documentation updated
• CHANGELOG.md updated (only for user relevant changes)
• author name in AUTHORS

[codecov]

Codecov Report

Merging #1126 (1a821e0) into master (fc291ce) will increase coverage by 0.26%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1126      +/-   ##
==========================================
+ Coverage   96.59%   96.86%   +0.26%     
==========================================
  Files          32       31       -1     
  Lines        1794     1789       -5     
==========================================
  Hits         1733     1733              
+ Misses         61       56       -5     

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[Andrew-Chen-Wang]

recommendation: Add the function to a utils file and describe how to use it in the docs and docstring.

[n2ygk]

recommendation: Add the function to a utils file and describe how to use it in the docs and docstring.

I've added a new Tutorial in #1128 that addresses this.