tests/xwayland: Remove manual timeout implementation

One of the best things about a real test framework is that they handle
timeouts for you.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Reported-by: Simon Ser <contact@emersion.fr>

tests/xwayland-test.c

@@ -108,7 +108,6 @@ TEST(xwayland_client_test)
 	XSelectInput(display, window, ExposureMask);
 	XMapWindow(display, window);
 
-	alarm(4);
 	while (1) {
 		XNextEvent(display, &event);
 		if (event.type == Expose)