Use MissingAnnotationEmptyState for plugins (#2824)

plugins/kubernetes/src/Router.tsx

@@ -20,7 +20,7 @@ import { Route, Routes } from 'react-router-dom';
 
 import { rootCatalogKubernetesRouteRef } from './plugin';
 import { KubernetesContent } from './components/KubernetesContent';
-import { WarningPanel } from '@backstage/core';
+import { MissingAnnotationEmptyState } from '@backstage/core';
 
 const KUBERNETES_ANNOTATION = 'backstage.io/kubernetes-id';
 
@@ -29,11 +29,7 @@ export const Router = ({ entity }: { entity: Entity }) => {
     entity.metadata.annotations?.[KUBERNETES_ANNOTATION];
 
   if (!kubernetesAnnotationValue) {
-    return (
-      <WarningPanel title="Kubernetes plugin:">
-        <pre>{KUBERNETES_ANNOTATION}</pre> annotation is missing on the entity.
-      </WarningPanel>
-    );
+    return <MissingAnnotationEmptyState annotation={KUBERNETES_ANNOTATION} />;
   }
 
   return (