Remove unused ChooserUtil.java

The helper methods provided by this class have been unused
since ag/13807667 (part of removing the old ChooserTargetService
functionality).

Test: http://cs/search?q=chooserutil&sq=package:android-internal
Bug: 148416928
Change-Id: I0aaaa5f597ef72097f1847a3187b335791287a60