Pin Nextcloud version to current stable release

roles/nextcloud/defaults/main.yml

@@ -1,7 +1,7 @@
 ---
 
 # set preferred application version
-nextcloud_version: fpm-alpine
+nextcloud_version: 27-fpm-alpine
 # set preferred postgres version
 nextcloud_db_version: 12-alpine
 
@@ -41,4 +41,3 @@ nextcloud_smtp_from_domain: "{{ server_domain }}"
 # nextcloud_s3_ssl: true
 # nextcloud_s3_region: eu-central-1
 # nextcloud_s3_usepath_style: true
-