Cleanup the useDebouncedEffect experiment

Summary:
This diff cleans up the `use_debounced_effects_for_animated` experiment. It is not shipped because it breaks semantics of Animated.

It also removes the implementation of now unused `useDebouncedEffect` hook.

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Details here https://fb.workplace.com/groups/3611662615830335/permalink/3666119690384627/

Changelog: [Internal]

Reviewed By: bvanderhoof

Differential Revision: D62188361

fbshipit-source-id: ce215cf7dd57e41e02c33760e91808d774bbd919