Reduce the size increase for the ExpandPipOnPinchOpenTest

Previously the test would resize above the max allowed size, which in
turn would make the auto resize logic bring it back to maximum allowed
size.

In such cases the PiP would increase at first, but then would shrink to
fit on the screen, causing the test to fail.

Change-Id: Ieb96d4ba2b607a3e2b9821f13e909acaaf6d31c3
Test: atest WMShellFlickerTests:ExpandPipOnPinchOpenTest
Bug: 275292932