Relax bounds check in desktop entry flicker tests

The current intial bounds check is very flaky. Both the size and
position of the inital bounds are extensivly covered by unit tests so we
can relax this check to simply verify the app window is within the
display bounds when entering desktop.

Flag: EXEMPT test fix
Test: atest EnterDesktopFromKeyboardShortcutFlickerTest, atest
EnterDesktopWithDragFlickerTest
Bug: 437536491

Change-Id: Ia0ae14dd8ca2e9e94a1fd03ad6ccbe8730f84f58