use https instead of ssh for submodule

[sanposhiho]

Jobs post-kube-scheduler-simulator-push were failed.
https://prow.k8s.io/view/gs/kubernetes-jenkins/logs/post-kube-scheduler-simulator-push-images/1456617270737375232

error log:

$ git submodule update --init --recursive
Submodule 'submodules/kubernetes' (git@github.com:kubernetes/kubernetes.git) registered for path 'submodules/kubernetes'
Cloning into '/home/prow/go/src/github.com/kubernetes-sigs/kube-scheduler-simulator/submodules/kubernetes'...
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
fatal: clone of 'git@github.com:kubernetes/kubernetes.git' into submodule path '/home/prow/go/src/github.com/kubernetes-sigs/kube-scheduler-simulator/submodules/kubernetes' failed
Failed to clone 'submodules/kubernetes'. Retry scheduled
Cloning into '/home/prow/go/src/github.com/kubernetes-sigs/kube-scheduler-simulator/submodules/kubernetes'...
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
fatal: clone of 'git@github.com:kubernetes/kubernetes.git' into submodule path '/home/prow/go/src/github.com/kubernetes-sigs/kube-scheduler-simulator/submodules/kubernetes' failed
Failed to clone 'submodules/kubernetes' a second time, aborting
# Error: exit status 1

I also asked it on test-infra: kubernetes/test-infra#24268

[sanposhiho]

/kind bug

[sanposhiho]

/label tide/merge-method-squash

[Huang-Wei]

/lgtm

[sanposhiho]

/approve

Let's check if job works or not with this change.

[k8s-ci-robot]

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This pull-request has been approved by: sanposhiho

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[sanposhiho]

Nice, error log is changed.

Running...
$ARTIFACTS is set, sending logs to /logs/artifacts
2021/12/07 04:41:43 Build directory: .
2021/12/07 04:41:43 /home/prow/go/src/github.com/kubernetes-sigs/kube-scheduler-simulator/cloudbuild.yaml does not exist

https://prow.k8s.io/view/gs/kubernetes-jenkins/logs/post-kube-scheduler-simulator-push-images/1468077827424260096

This error is Okay. We'll create cloudbuild.yaml in #21