fix(alertrules): avoid making alert rules readonly in UI when updated

[jarmd]

This will fix, so existent alert rule will not move into "Provisioned" state when updated by a restore.

This has been tested on our staging and production environment, by using the following forked version: https://github.com/vestas-oss/grafana-backup-tool

1 thing to add is that IF someone has run the restore before this fix, the alarts will keep staying in provisioning mode, and the only way to correct this is to delete all alert rules using the grafana API:

• curl -k -X DELETE -H "Content-Type: application/json" -H "Authorization: Bearer 1234 " 'https://your-grafana.net/api/v1/provisioning/alert-rules/ID'