xwayland: require xcb-icccm

This dependency is already required by many other widely used X11
programs, such as i3, Qt, and other XWMs. So it should be available
on most systems.

X11 support can be pretty broken without xcb-icccm, with focus issues
for instance. Let's just remove this --please-break-my-desktop footgun
option.

meson.build

@@ -87,7 +87,6 @@ features = {
 	'x11-backend': false,
 	'xwayland': false,
 	'xcb-errors': false,
-	'xcb-icccm': false,
 	'xdg-foreign': false,
 }