Fix duplicate variable override (`matrix_wechat_container_image_registry_prefix_upstream`)

group_vars/matrix_servers

@@ -2071,7 +2071,7 @@ matrix_wechat_systemd_required_services_list_auto: |
 
 matrix_wechat_container_image_registry_prefix_upstream: "{{ matrix_container_global_registry_prefix_override if matrix_container_global_registry_prefix_override else matrix_wechat_container_image_registry_prefix_upstream_default }}"
 
-matrix_wechat_container_image_registry_prefix_upstream: "{{ matrix_container_global_registry_prefix_override if matrix_container_global_registry_prefix_override else matrix_wechat_agent_container_image_registry_prefix_upstream_default }}"
+matrix_wechat_agent_container_image_registry_prefix_upstream: "{{ matrix_container_global_registry_prefix_override if matrix_container_global_registry_prefix_override else matrix_wechat_agent_container_image_registry_prefix_upstream_default }}"
 
 matrix_wechat_container_image_self_build: "{{ matrix_architecture not in ['amd64', 'arm64'] }}"