xwayland: send focus change event unconditionally
Created by: Xyene
This fixes issues with (at least) dialogs in Jetbrains IDEs becoming
unclickable if they ever lost focus (ref. swaywm/sway#5373). Prior to
this change, since xwm->focus_surface
would be set prior to
xwm_surface_activate
being called, the latter would short-circuit
immediately and not notify the application of the focus change.