fix(monitoring): ignore openapi discovery in apiserver latency alert

KubernetesApiServerLatency fired continuously on the p99 of
apiserver_request_duration_seconds_bucket. Every firing series was
verb="GET", subresource="openapi/v3" (kubelet, kube-controller-manager,
kube-scheduler, apiserver) at ~8s, while real verbs (POST/LIST/DELETE)
stay around 0.2s.

openapi/v3 is a streaming discovery endpoint, like WATCH, so exclude
subresource=~"^openapi/" from the rule.

hosts/12kingdoms-youko/homelab-services/monitoring/alert_rules/kube-state-metrics-exporter.yml

@@ -422,7 +422,7 @@ groups:
       - alert: KubernetesApiServerLatency
         expr:
           'histogram_quantile(0.99,
-          sum(rate(apiserver_request_duration_seconds_bucket{subresource!="log",verb!~"^(?:CONNECT|WATCHLIST|WATCH|PROXY)$"}
+          sum(rate(apiserver_request_duration_seconds_bucket{subresource!="log",subresource!~"^openapi/",verb!~"^(?:CONNECT|WATCHLIST|WATCH|PROXY)$"}
           [10m])) WITHOUT (instance, resource)) > 1'
         for: 2m
         labels: