wayland: Do not map toplevel utility as popup

Applications can specify the type hint as utility even on toplevel
windows.

When that toplevel is also marked as a transient for another window,
GDK Wayland backend would translate that as an xdg_popup which is not
appropriate.

While utility temp windows should remain mapped as subsurfaces (such as
the ones used by treeviews), regular windows should not translate as
neither a subsurface nor an xdg_popup.

https://bugzilla.gnome.org/show_bug.cgi?id=781945

gdk/wayland/gdkwindow-wayland.c

@@ -2246,11 +2246,6 @@ should_map_as_popup (GdkWindow *window)
     case GDK_WINDOW_TYPE_HINT_COMBO:
       return TRUE;
 
-    case GDK_WINDOW_TYPE_HINT_UTILITY:
-      if (GDK_WINDOW_TYPE (window) != GDK_WINDOW_TEMP)
-        return TRUE;
-      break;
-
     default:
       break;
     }