gdk/display-wayland: Don't bypass portal for theme entries

When commit 49589e1da added support for the new high-contrast key,
it missed that the getter should only use the setting directly when
not going through the portal.

https://gitlab.gnome.org/GNOME/gtk/-/issues/4593

gdk/wayland/gdkdisplay-wayland.c

@@ -2110,7 +2110,11 @@ set_theme_from_entry (GdkDisplay       *display,
   GSettingsSchema *schema = NULL;
   gboolean hc = FALSE;
 
-  settings = (GSettings *)g_hash_table_lookup (display_wayland->settings, "org.gnome.desktop.a11y.interface");
+  if (display_wayland->settings_portal == NULL)
+    {
+      settings = (GSettings *)g_hash_table_lookup (display_wayland->settings,
+                                                   "org.gnome.desktop.a11y.interface");
+    }
 
   if (settings)
     g_object_get (settings, "settings-schema", &schema, NULL);