Comparing dimension and rotation instead of DisplayInfo

DisplayInfo.equals is too much and only dimension/rotation changes
should be concerned in PinnedStackController#onTaskStackBoundsChanged

This regression is introduced in ag/6971276

Bug: 131418250
Test: Manual test PiP with YT / GMM
Change-Id: I6f29fd2b7606e3e44d88003bcae511e4afea3d30