Automatic merge from submit-queue (batch tested with PRs 60196, 59844, 60255, 60254, 60251). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Remove k8s prefix from gcr.io/k8s-ingress-gce-image-push repo

**What this PR does / why we need it**:
Was causing e2e tests to fail. 

**Release note**:

```release-note
None
```

/assign @MrHohn