fix: Properties dropped using None or __NULL__ in stream maps are now also removed from the schema required array

[edgarrmondragon]

Closes #2662.

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📚 Documentation preview 📚: https://meltano-sdk--2663.org.readthedocs.build/en/2663/

[codspeed-hq]

CodSpeed Performance Report

Merging #2663 will not alter performance

_{Comparing 2662-bug-using-stream-maps-to-remove-a-property-doesnt-drop-it-from-the-json-schema-required-array (59c5f7e) with main (f465705)}

Summary

✅ 6 untouched benchmarks

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.86%. Comparing base (f465705) to head (59c5f7e).
Report is 113 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2663      +/-   ##
==========================================
+ Coverage   89.82%   89.86%   +0.04%     
==========================================
  Files          58       58              
  Lines        4886     4886              
  Branches      960      960              
==========================================
+ Hits         4389     4391       +2     
+ Misses        346      344       -2     
  Partials      151      151              

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