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.