Fix syntax error on cloudbuild.yaml

[sanposhiho]

Hello.
Sorry, I forgot to add ' at some ends on cloudbuild.yaml in #21 🤦‍♂️

ERROR: (gcloud.builds.submit) parsing /home/prow/go/src/github.com/kubernetes-sigs/kube-scheduler-simulator/cloudbuild.yaml: while parsing a block collection
  in "/home/prow/go/src/github.com/kubernetes-sigs/kube-scheduler-simulator/cloudbuild.yaml", line 29, column 3
expected <block end>, but found '<scalar>'
  in "/home/prow/go/src/github.com/kubernetes-sigs/kube-scheduler-simulator/cloudbuild.yaml", line 31, column 6

https://prow.k8s.io/view/gs/kubernetes-jenkins/logs/post-kube-scheduler-simulator-push-images/1468300940288200704

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sanposhiho

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Details

Needs approval from an approver in each of these files:

• OWNERS [sanposhiho]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[sanposhiho]

/label tide/merge-method-squash
/kind bug

[haosdent]

/lgtm