Rename a bunch of playbook variables for better consistency

roles/matrix-server/tasks/setup_nginx_proxy.yml

@@ -36,7 +36,7 @@
 #
 - name: Ensure nginx Docker image is pulled
   docker_image:
-    name: "{{ docker_nginx_image }}"
+    name: "{{ matrix_docker_image_nginx }}"
   when: matrix_nginx_proxy_enabled
 
 - name: Allow access to nginx proxy ports in firewalld
@@ -87,4 +87,4 @@
   file:
     path: "/etc/cron.d/matrix-nginx-proxy-periodic-restarter"
     state: absent
-  when: "not matrix_nginx_proxy_enabled"
+  when: "not matrix_nginx_proxy_enabled"