Prevent dismissing split when pausing tasks trampolines to new activity

* This was originally done in ag/23352436 for the case of swiping up
split to home and imemidately opening up one of the split tasks in
fullscreen. Removing this code doesn't cause that to repro anymore
* This is a partial fix, more to be done with b/395146421

Test: Bug doesn't repro, old bug doesn't repro for which this
code was added
Fix: 339769621
Flag: EXEMPT bugfix

Change-Id: I0d7f8a7070bcd7ed3ecf5350299f1914e7799247