refine the alert expression

* Remove the "name" label which is removed in the metric
* Use `last_over_time` to still get values after resetting

Author: hongkailiu

install/0000_90_cluster-version-operator_02_prometheusrule-TechPreviewNoUpgrade.yaml

@@ -20,7 +20,7 @@ spec:
         description: The conditional update risk {{ "{{ $labels.risk }}" }} applies to the cluster, and the cluster update to a version exposed to the risk is not recommended. For more information refer to 'oc adm upgrade'.
         runbook_url: https://github.com/openshift/runbooks/blob/master/alerts/cluster-monitoring-operator/OpenShiftUpdateRiskApplies.md
       expr: |
-        max by (namespace, name, risk) (cluster_version_risk_conditions{job="cluster-version-operator", name="version", condition="Applies"} == 1)
+        max by (namespace, risk) (last_over_time(cluster_version_risk_conditions{job="cluster-version-operator", condition="Applies"}[5m]) == 1)
       for: 10m
       labels:
         severity: warning