Stop emitting deprecated onTextInput events (#44479)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/44479

TextInputs' onTextInput callback was removed way back in React Native 0.62 with https://github.com/facebook/react-native/commit/3f7e0a2c9601fc186f25bfd794cd0008ac3983ab , but remnants of the implementation exists.

We first have to remove the event emitting in native code, and can land the full removal separately in D57092733, once there's no older client references remaining to this event.

Changelog: [General][Removed] Remove deprecated onTextInput callback

Reviewed By: cipolleschi

Differential Revision: D57092734

fbshipit-source-id: 5b0beee3d55b70717216fe8ceaf52444540f5adc