Fix `ddclient_container_image_registry_prefix_upstream`

Closes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/5165

Signed-off-by: Suguru Hirahara <did🔑z6MkvVZk1A3KBApWJXv2Ju4H14ErDfRGxh8zxdXSZ4vACDg5>

group_vars/matrix_servers

@@ -3681,7 +3681,7 @@ ddclient_uid: "{{ matrix_user_uid }}"
 ddclient_gid: "{{ matrix_user_gid }}"
 
 ddclient_container_image_registry_prefix: "{{ 'localhost/' if ddclient_container_image_self_build else ddclient_container_image_registry_prefix_upstream }}"
-ddclient_container_image_registry_prefix_upstream: "{{ matrix_container_global_registry_prefix_override if matrix_container_global_registry_prefix_override else ddclient_docker_image_registry_prefix_upstream_default }}"
+ddclient_container_image_registry_prefix_upstream: "{{ matrix_container_global_registry_prefix_override if matrix_container_global_registry_prefix_override else ddclient_container_image_registry_prefix_upstream_default }}"
 
 ddclient_web: "https://cloudflare.com/cdn-cgi/trace"