fix(dependency_getter): handle strings for setuptools dynamic dependencies

[mkniewallner]

Closes #944.

PR Checklist

• A description of the changes is added to the description of this PR.
• If there is a related issue, make sure it is linked to this PR.
• If you've fixed a bug or added code that should be tested, add tests!
• If you've added or modified a feature, documentation in docs is updated

Description of changes

It might not be obvious from setuptools documentation, but file attribute can either be a string or a list of strings.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.0%. Comparing base (40765df) to head (4cab592).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #945   +/-   ##
=====================================
  Coverage   93.0%   93.0%           
=====================================
  Files         37      37           
  Lines        991     994    +3     
  Branches      97      98    +1     
=====================================
+ Hits         922     925    +3     
  Misses        55      55           
  Partials      14      14           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.