api: add api-approved.kubernetes.io annotation to CRD

This commit adds the following annotation
`api-approved.kubernetes.io: \
"https://github.com/kubernetes-csi/external-snapshot-metadata/pull/2"`.

Refer to kubernetes/enhancements#1111
for more details.

Signed-off-by: Rakshith R <rar@redhat.com>

client/config/crd/cbt.storage.k8s.io_snapshotmetadataservices.yaml

@@ -4,6 +4,7 @@ kind: CustomResourceDefinition
 metadata:
   annotations:
     controller-gen.kubebuilder.io/version: v0.15.0
+    api-approved.kubernetes.io: "https://github.com/kubernetes-csi/external-snapshot-metadata/pull/2"
   name: snapshotmetadataservices.cbt.storage.k8s.io
 spec:
   group: cbt.storage.k8s.io