Do not remove surface when resetting previous PiP

This was introduced in ag/23617718 and is no longer needed.

However, with this change we are now hitting ag/21485364 and the
initial activity ends up being sent to the back instead to front.

Follow up will require handling this special case setup of
activity with singleInstance launchMode.

Bug: 296071915
Bug: 285231679
Test: manually, follow steps in b/285231679 with no regression found
Test: manually, follow repro steps using modified sample app - no crash
Change-Id: I83c3a0456c8508ab470da98537d27dc1dc1b74f2