window: Increase the height of CSD titlebars

This seems to be more accurate with what we currently see in
GNOME. Without having the app expose this information to us, it might be
a better idea to use the default frame style for this information instead.

src/core/window.c

@@ -4165,7 +4165,7 @@ meta_window_get_titlebar_rect (MetaWindow    *window,
     {
       /* Pick an arbitrary height for a titlebar. We might want to
        * eventually have CSD windows expose their borders to us. */
-      rect->height = 15;
+      rect->height = 50;
     }
 }