Alt PiP resize bounds no smaller than minimal

As a work around, we minus the PiP bounds bottom by one pixel to address
the flicker when resizing with no actual bounds change. This in turn
would cause the final bounds being smaller than the allowed minimum.

Change this by adding one pixel instead.

Flag: com.android.wm.shell.enable_pip2
Bug: 383602326
Bug: 380030822
Test: atest --iteration 10 PinnedStackTests#testEnterPipWithMinimalSize
Change-Id: I0027f953177e4d0d3db0102801a68ac9538111c2