dillon1000/react

Remove useMutationEffect (#14336)

useMutationEffect has problems (namely, refs aren't attached at the time that it runs) and we're not positive it's necessary. useLayoutEffect runs at the same time as componentDidMount/Update so it's sufficient for all existing use cases; it can be used in any case that useEffect happens too late. Until we figure out what we want to do, let's delete it.