* Alerting: Clear alerting rule evaluation errors after intermittent failures
When an alert transitioned in a way that `alerting -> error -> (alerting|nodata)`, the error provided by the `error` state would never be cleared thus the API and UI would show the health as an error.
(cherry picked from commit dd5a2e5128)
Co-authored-by: gotjosh <josue@grafana.com>