Breaking: Don't try to auto-detect the workflow engine

[Andrew-S-Rosen]

Summary of Changes

Previously, quacc would try to auto-detect which workflow engine you had installed and then set that as the default. This, however, is too smart for its own good. It often leads to user confusion because if you install (say) atomate2 and get jobflow installed as a side-effect, it will auto-change to jobflow without the user knowing. This behavior has been disabled. As noted in the docs, the user should specific explicitly which workflow engine to use.

Checklist

• I have read the "Guidelines" section of the contributing guide. Don't lie! 😉
• My PR is on a custom branch and is not named main.
• I have added relevant, comprehensive unit tests.

Notes

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• If you are an external contributor, you will see a comment from @buildbot-princeton. This is solely for the maintainers.
• When your code is ready for review, ping one of the active maintainers.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.06%. Comparing base (43fd98f) to head (3f7dd96).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2124      +/-   ##
==========================================
- Coverage   99.06%   99.06%   -0.01%     
==========================================
  Files          81       81              
  Lines        3320     3318       -2     
==========================================
- Hits         3289     3287       -2     
  Misses         31       31              

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