Clean up "enablePreciseSchedulingForPremountItemsOnAndroid" feature flag (#49841)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/49841

Changelog: [internal]

This effectively reverts D62962341 / https://github.com/facebook/react-native/pull/46563 as the experiments didn't provide the expected wins and we don't have bandwidth to iterate on this.

Reviewed By: rshest

Differential Revision: D70622429

fbshipit-source-id: c53c9437448c0a7be8f5b4f04d6369efbd99105a