replace str() with repr() in StringEnum & test it (#1369)

[teks]

Related Issue(s):

• str/repr mixup in StringEnum? #1369

Description: Simple replacement of str() with repr(). This technically changes the output from a string to a quoted string, eg foo to 'foo'. But I couldn't find any places where it'd matter.

This is such a minor change I wasn't sure whether to add to the changelog; should I?

PR Checklist:

• Pre-commit hooks and tests pass (run scripts/test)
• Documentation has been updated to reflect changes, if applicable
• This PR maintains or improves overall codebase code coverage.
• Changes are added to the CHANGELOG. See the docs for information about adding to the changelog.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.17%. Comparing base (b052b2a) to head (8255cb7).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1473      +/-   ##
==========================================
+ Coverage   91.15%   91.17%   +0.01%     
==========================================
  Files          52       52              
  Lines        7251     7251              
  Branches      875      875              
==========================================
+ Hits         6610     6611       +1     
+ Misses        461      460       -1     
  Partials      180      180              

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[gadomski]

This is such a minor change I wasn't sure whether to add to the changelog; should I?

Nah, doesn't need one. Thanks!