Replace all exact React.Element type in react-native with ExactReactElement_DEPRECATED (#45998)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/45998

The exact `React.Element` type is deprecated and will be removed in a future version of Flow.

Changelog: [Internal]

Reviewed By: gkz

Differential Revision: D61205640

fbshipit-source-id: a029a3a46c7d8d9f94b0b931b991b2ce461151b2