Add missing `:` to `matrix_media_repo_redis_shards` entry

Ref: https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/4851#issuecomment-3732696383

group_vars/matrix_servers

@@ -3724,7 +3724,7 @@ matrix_media_repo_redis_shards: |
   {{
     ([{
           'name': 'valkey',
-          'addr': (valkey_identifier + valkey_container_http_port | string),
+          'addr': (valkey_identifier + ':' + valkey_container_http_port | string),
     }])
     if valkey_enabled and matrix_media_repo_redis_enabled
     else []