Do not send setFinishTaskTransaction if not swipe

In PiP2, there is no need to send setFinishTaskTransaction()
unless we are swiping PiP to home.

This is because either ATMS#enterPictureInPictureMode() is supposed
to request a TRANSIT_PIP as the activity goes to pause.

Bug: 380515865
Flag: com.android.wm.shell.enable_pip2
Test: repro the steps in the bug
Change-Id: Ic24c0c0f471179198a5fe3221971cf5b6d634797