Ensure database port is passed to Borg as an integer

Without this, it's a string and borg says:

> At 'hooks.postgresql_databases[INDEX_HERE].port': '5432' is not of type 'integer'
> /etc/borgmatic/config.yaml /etc/borgmatic.d /tmp/.config/borgmatic/config.yaml /tmp/.config/borgmatic.d: No valid configuration files found

.. and fails to do anything.

roles/custom/matrix-backup-borg/templates/config.yaml.j2

@@ -34,7 +34,7 @@ hooks:
     hostname: {{ matrix_backup_borg_postgresql_databases_hostname|to_json }}
     username: {{ matrix_backup_borg_postgresql_databases_username|to_json }}
     password: {{ matrix_backup_borg_postgresql_databases_password|to_json }}
-    port: {{ matrix_backup_borg_postgresql_databases_port|to_json }}
+    port: {{ matrix_backup_borg_postgresql_databases_port | int | to_json }}
   {% endfor %}
 {% endif %}
   after_backup: