This diff will be reverted after the React Native 0.72 upgrade (tracked in ENG-5892). This diff needs to exist because I'm landing the Flow 0.202 upgrade before the React Native 0.72 upgrade.
It appears that Platform.select types are improved in later versions of React Native, and prior to those improvements these typehints are necessary.
NOTE: CI will fail on this diff, but only temporarily. Once ENG-5893 is resolved, we should expect it to pass.
Depends on D10045