Uninstall unused Webpack 4 packages (facebook#27058)

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## Summary

 - Remove unused webpack 4 dependencies

## How did you test this change?

 - Ran `yarn test --prod`
 - Ran `yarn test`

## Related PRs:
 - facebook#26887

package.json

@@ -97,7 +97,6 @@
     "tmp": "^0.1.0",
     "typescript": "^3.7.5",
     "web-streams-polyfill": "^3.1.1",
-    "webpack": "^4.41.2",
     "yargs": "^15.3.1"
   },
   "devEngines": {