Transform `mixed` to `unknown` in xplat/js (#55048)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/55048

Transform leftovers dropped by conflicts

Command:
```
js1 flow-runner codemod flow/transformUtilityType --legacy-type='mixed' --format-files=false xplat/js
```

drop-conflicts

Reviewed By: SamChou19815

Differential Revision: D90131601

fbshipit-source-id: 6497ce36dfed3b3ebe2706cf90909447b36e397a

Marco Wang committed 3mo ago

625d702fec0d0aa29953a8152219f9651f490dcd

Parent: d19efcf

Committed by meta-codesync[bot] <215208954+meta-codesync[bot]@users.noreply.github.com> on 1/6/2026, 8:08:06 PM