Update K8s version. (#1529)

Author: constanca-m

.buildkite/pipeline.yml

@@ -4,7 +4,7 @@ env:
   ELASTIC_PACKAGE_COMPOSE_DISABLE_ANSI: "true"
   ELASTIC_PACKAGE_COMPOSE_DISABLE_PULL_PROGRESS_INFORMATION: "true"
   KIND_VERSION: 'v0.20.0'
-  K8S_VERSION: 'v1.27.3'
+  K8S_VERSION: 'v1.28.0'
   LINUX_AGENT_IMAGE: "golang:${GO_VERSION}"
   WINDOWS_AGENT_IMAGE: "family/ci-windows-2022"