templates/docker-compose/docker-compose.yml - bump nextcloud to v31

Actual upgrade done one major version at a time.

templates/docker-compose/docker-compose.yml

@@ -56,7 +56,7 @@ services:
       - redis:/data
 
   nextcloud:
-    image: nextcloud:28-fpm-alpine
+    image: nextcloud:31-fpm-alpine
     restart: always
     volumes:
       - nextcloud_src:/var/www/html
@@ -76,7 +76,7 @@ services:
 #      test: ["CMD-SHELL", "wget -q --spider --proxy=off localhost:3000/health || exit 1"]
 
   nextcloud_cron:
-    image: nextcloud:28-fpm-alpine
+    image: nextcloud:31-fpm-alpine
     restart: always
     volumes:
       - nextcloud_src:/var/www/html