examples: Label the deployment to get it backed up (#6348)

Following the examples instructions[1], the nginx-deployment is not
backed up or restored. Add a label to the deployment so it will be
backed up and restored.

Similar change is needed for `examples/nginx-app/with-pv.yaml` but I did
not try that example.

[1] https://velero.io/docs/v1.11/contributions/minio/

Fixes #6347

Signed-off-by: Nir Soffer <nsoffer@redhat.com>

examples/nginx-app/base.yaml

@@ -26,6 +26,8 @@ kind: Deployment
 metadata:
   name: nginx-deployment
   namespace: nginx-example
+  labels:
+    app: nginx
 spec:
   replicas: 2
   selector: