Replace XDestroyWindow with xcb_destroy_window

Signed-off-by: Uli Schlachter <psychon@znc.in>

src/compton.c

@@ -5603,7 +5603,7 @@ session_destroy(session_t *ps) {
 
   // Free reg_win
   if (ps->reg_win) {
-    XDestroyWindow(ps->dpy, ps->reg_win);
+    xcb_destroy_window(c, ps->reg_win);
     ps->reg_win = None;
   }