autotests: Drop TestXdgShellClient::testWindowOpensLargerThanScreen()

With the xdg_toplevel.configure_bounds support, the compositor is finally able to tell the client the maximum recommended window size.

That approach allows us to keep the compositor side simple and it prevents (as long as the app is well behaved) annoying visual glitches such as mapping window with one size and then quickly resizing it to the final size.