Fix typeValidation in TransformOverride

[RustedBones]

Cherry-pick from #4962

Fix #4963

[codecov]

Codecov Report

Merging #4967 (6cb0fd8) into main (a39d157) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 6cb0fd8 differs from pull request most recent head 1753687. Consider uploading reports for the commit 1753687 to get more accurate results

@@           Coverage Diff           @@
##             main    #4967   +/-   ##
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  Coverage   63.08%   63.08%           
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  Files         282      282           
  Lines       10648    10649    +1     
  Branches      761      761           
=======================================
+ Hits         6717     6718    +1     
  Misses       3931     3931           

Files Changed	Coverage Δ
...a/com/spotify/scio/testing/TransformOverride.scala	100.00% <100.00%> (ø)