Revert "Introduce TaskFragment transition type"

This reverts commit 3f7830ea.

Reason for revert: Broke test android.server.wm.MultiDisplayPolicyTests#testAppTransitionForActivityOnDifferentDisplay on git_master on cf_x86_64_phone-userdebug

Bug: 197639726
Change-Id: I7705b36a3fa8de5ce98774c809a0cc309a08937c