Remove kubernetes manifest related code and tests (opea-project#1466)

Remove deprecated kubernetes manifest related code and tests.
k8s implementation for those examples based on helm charts will target for next release.

Signed-off-by: chensuyue <suyue.chen@intel.com>

Author: chensuyue

.github/workflows/push-infra-issue-creation.yml

@@ -54,6 +54,6 @@ jobs:
 
             ${{ env.changed_files }}
 
-            Please verify if the helm charts and manifests need to be changed accordingly.
+            Please verify if the helm charts need to be changed accordingly.
 
             > This issue was created automatically by CI.

ChatQnA/tests/common/_test_manifest_utils.sh

@@ -180,4 +180,3 @@ Utilizes the open-source platform **Keycloak** for single sign-on identity and a
 
 - **[Keycloak Configuration Guide](./docker_compose/intel/cpu/xeon/keycloak_setup_guide.md)**: Instructions to set up Keycloak for identity and access management.
 - **[Xeon Guide](./docker_compose/intel/cpu/xeon/README.md)**: Instructions to build Docker images from source and run the application via Docker Compose.
-- **[Xeon Kubernetes Guide](./kubernetes/intel/README.md)**: Instructions to deploy the application via Kubernetes.