Description of problem:
The sample nginx image "registry.hub.docker.com/nginx" need the authentication. Suggest use one nginx image that doesn't need the authentication such as:"docker.io/nginx".

Version-Release number of selected component (if applicable):
1.operator-sdk version:  
"v1.8.0-ocp", commit: "016423f32c9757a10dc7a9e953818bc20ae3eba4", kubernetes version: "v1.20.2", go version: "go1.14.12", GOOS: "linux", GOARCH: "amd64"

2.cluster version:
4.8.0-0.nightly-2021-06-07-034343   True        False         15h     Cluster version is 4.8.0-0.nightly-2021-06-07-034343

How reproducible:
always

Steps to Reproduce:
generate the helm operator by https://docs.openshift.com/container-platform/4.7/operators/operator_sdk/helm/osdk-helm-tutorial.html
1.$mkdir -p $HOME/projects/nginx-operator 
2.$cd $HOME/projects/nginx-operator
3.$operator-sdk init --plugins=helm --domain=example.com --group=demo --version=v1 --kind=Nginx
4.$make install run
5.$oc apply -f config/samples/demo_v1_nginx.yaml

Actual results:
The nginx image can't be downloaded.
$ oc describe pod nginx-sample-7d765fb9cf-df7j5
  Warning  Failed          77m (x4 over 78m)      kubelet            Failed to pull image "nginx:1.16.0": rpc error: code = Unknown desc = Error reading manifest 1.16.0 in registry.hub.docker.com/nginx: unauthorized: authentication required

Expected results:
The sample nginx can run well.

Additional info: