grocy: Add docker hostname to backup container

roles/grocy/templates/docker-compose.yaml.j2

@@ -19,6 +19,7 @@ services:
 {% if restic_enable is not undefined and not false and stack_grocy_restic_enable is not undefined and not false %}
   backup:
     image: mazzolino/restic
+    hostname: "{{ ansible_hostname }}"
     environment:
       TZ: "{{ restic_tz }}"
       BACKUP_CRON: "{{ stack_grocy_restic_cron }}"