Remove old Prow image pushing job.

The new image pushing job has been running successfully for a few months
and publishes images to a new location (`post-k8s-infra-prow-images`, to
us-docker.pkg.dev/k8s-infra-prow/images). There should be no use of
these images remaining within the kubernetes org once blocking PRs are
submitted, so this job should be fine to turn down.

config/jobs/kubernetes-sigs/prow/prow-postsubmits.yaml

@@ -34,49 +34,3 @@ postsubmits:
       testgrid-dashboards: sig-testing-prow-repo
       testgrid-tab-name: post-test-verify
       description: Runs 'make test verify' on the prow repo on each commit
-
-### Trusted Jobs ###
-
-  - name: post-push-prow
-    cluster: test-infra-trusted
-    # Runs on more than just the Prow dir to include some additional images that we publish to gcr.io/k8s-prow.
-    skip_if_only_changed: '^site/'
-    decorate: true
-    labels:
-      # Building deck requires docker for typescript compilation.
-      preset-dind-enabled: "true"
-    branches:
-    - ^main$
-    max_concurrency: 1
-    spec:
-      serviceAccountName: pusher
-      containers:
-      - image: gcr.io/k8s-staging-test-infra/kubekins-e2e:v20240725-1d8ea3e909-test-infra
-        command:
-        - runner.sh
-        args:
-        - make
-        - push-images
-        env:
-        # docker-in-docker needs privileged mode
-        securityContext:
-          privileged: true
-        resources:
-          requests:
-            cpu: "15"
-      tolerations:
-      - key: "highcpu"
-        operator: "Equal"
-        value: "true"
-        effect: "NoSchedule"
-      nodeSelector:
-        highcpu: "true"
-    annotations:
-      testgrid-dashboards: sig-testing-prow-repo
-      testgrid-tab-name: push-images-legacy
-      testgrid-alert-email: [email protected], [email protected]
-      testgrid-num-failures-to-alert: '1'
-      description: Builds and pushes all prow container images on each commit by running make push-images
-    rerun_auth_config:
-      github_users:
-      - alvaroaleman