Actually run backup rotation in [email protected]

Dry run example:

```shell
Dry run. No changes will be made.

Used space: 30 files, 133682908 bytes
Freed space: 34 files, 151342898 bytes
```

roles/postgres/templates/postgres-backups@.service.j2

@@ -9,4 +9,4 @@ Group = postgres
 WorkingDirectory = {{ postgres_backups_dir }}
 ExecStartPre = +/usr/bin/chown postgres:postgres {{ postgres_backups_dir }}
 ExecStart = /usr/bin/bash -c "/usr/bin/pg_dump --compress=9 --no-owner --format=p --file=%i_$(TZ=UTC date +%%Y%%m%%d-%%H%%M%%S).sql.gz %i"
-ExecStartPost = /usr/bin/python3 /usr/local/bin/rotate.py --keep 30 --dir {{ postgres_backups_dir }}
+ExecStartPost = /usr/bin/python3 /usr/local/bin/rotate.py --no-dry-run --keep 30 --dir {{ postgres_backups_dir }}