Remove legacy Paper renderer shim cleanup from artifact commit workflow (#36297)

## Summary

PR #36285 deleted the Paper (legacy) renderer, including the shim file
`scripts/rollup/shims/react-native/ReactNative.js`. However, the
`runtime_commit_artifacts` workflow still tries to `rm` this file after
moving build artifacts into `compiled-rn/`. Since the file no longer
exists in the build output, `rm` (without `-f`) fails and kills the
entire step.

This has caused **every run of the Commit Artifacts workflow to fail
since #36285 landed on April 16**, blocking both `builds/facebook-www`
and `builds/facebook-fbsource` branches from receiving new build
artifacts. This in turn blocks DiffTrain from syncing React changes into
Meta's internal monorepo.

.github/workflows/runtime_commit_artifacts.yml

@@ -167,10 +167,6 @@ jobs:
           # Delete the OSS renderers, these are sync'd to RN separately.
           RENDERER_FOLDER=$BASE_FOLDER/react-native-github/Libraries/Renderer/implementations/
           rm $RENDERER_FOLDER/ReactFabric-{dev,prod,profiling}.js
-          
-          # Delete the legacy renderer shim, this is not sync'd and will get deleted in the future.
-          SHIM_FOLDER=$BASE_FOLDER/react-native-github/Libraries/Renderer/shims/
-          rm $SHIM_FOLDER/ReactNative.js
 
           # Copy eslint-plugin-react-hooks
           # NOTE: This is different from www, here we include the full package