Cleanup exports for PressableExample in RN-Tester (#45294)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/45294

Just doing some cleanup here as those exports are scattered around this file.

Changelog:
[Internal] [Changed] - Cleanup exports for PressableExample in RN-Tester

Reviewed By: yungsters

Differential Revision: D59376617

fbshipit-source-id: 0f6f81fca7b5cbcdc05bbb6a1f87d3ad74c20b50