fix: plugins/kubernetes-backend/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-AJV-15274295

Author: snyk-io[bot]

plugins/kubernetes-backend/package.json

@@ -62,7 +62,7 @@
     "@backstage/integration-aws-node": "workspace:^",
     "@backstage/plugin-auth-node": "workspace:^",
     "@backstage/plugin-catalog-node": "workspace:^",
-    "@backstage/plugin-kubernetes-common": "workspace:^",
+    "@backstage/plugin-kubernetes-common": "0.2.8",
     "@backstage/plugin-permission-common": "workspace:^",
     "@backstage/plugin-permission-node": "workspace:^",
     "@google-cloud/container": "^4.0.0",