kill RCTRootViewIntegrationTests (#38871)

Summary:
Pull Request resolved: #38871

Changelog: [Internal]

these tests are the last callsite where we are getting event emitter off of RCTRootView... these particular tests have been disabled and they're like 8 years old, sooooooo i think it's just easier for me to delete them

Reviewed By: cipolleschi

Differential Revision: D48179389

fbshipit-source-id: 350e4be3bec439ebe9648b52dd6bd916e07c39a6

Author: philIip