osc: ensure tick after any mouse-event

Previously tick() was ensured unconditionally only after mouse-move,
but there are other mouse-events which need re-rendering (tick), like
mouse-down (icons may get grayed-out) or mouse-up (icons may change).

For instance: mpv --pause --myclip.mkv

then move the mouse over the volume/mute OSC button, then - without
moving the mouse - press and release the left mouse button.

The osc was not re-rendered because it's paused and the mouse didn't
move, so the volume icon didn't get grayed-out when held down, and the
icon doesn't change on mouse-up (to reflect the new mute state).

Now both these changes are rendered correctly.

player/lua/osc.lua

@@ -2486,8 +2486,10 @@ function process_event(source, what)
         if element_has_action(elements[n], action) then
             elements[n].eventresponder[action](elements[n])
         end
-        request_tick()
     end
+
+    -- ensure rendering after any (mouse) event - icons could change etc
+    request_tick()
 end