[android] Remove android fbjni subproject (#39691)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39691
After switching on using fbjni-java-only dependency, we do not need to have gradle subproject fbjni.
Test Plan: Imported from OSS
Differential Revision: D22054575
Pulled By: IvanKobzarev
fbshipit-source-id: 331478a57dd0d0aa06a5ce96278b6c897cb0ac78
