xdg-shell: Fix documentation
xdg-shell: Fix documentation

request_change_state has been folded into the configure event.

kwm81/weston,jonnylamb/weston,krezovic/weston,kwm81/weston,mchalupa/weston,xorgy/weston,xorgy/weston,Fantu/compositor-spice,krezovic/weston,Gnurou/weston,Gnurou/weston,mchalupa/weston,sir-murray/weston,giucam/weston,sir-murray/weston,Fantu/compositor-spice,Tarnyko/weston-xdg_surface_present,udoprog/weston,eyolfson/weston,Fantu/compositor-spice,udoprog/weston,eyolfson/weston,Tarnyko/weston-xdg_surface_present,jonnylamb/weston,giucam/weston