prow: reapply regsitry-pull preset (#78007)

On two previous attempts this change was [reverted](416f39d)
by a misbehaving `private-prow-configs-mirror` tool. This should be
fixed now, so we should be able to reapply.

Author: petr-muller

core-services/prow/02_config/_config.yaml

@@ -596,6 +596,18 @@ plank:
       index .Spec.Refs.Pulls 0}}{{.Number}}{{end}}). [Your PR dashboard](https://qe-private-deck-ci.apps.ci.l2s4.p1.openshiftapps.com/pr?query=is:pr+state:open+author:{{with
       index .Spec.Refs.Pulls 0}}{{.Author}}{{end}}).'
 pod_namespace: ci
+presets:
+- env: null
+  labels:
+    presets.ci.openshift.io/registry-pull: "true"
+  volumeMounts:
+  - mountPath: /etc/pull-secret
+    name: pull-secret
+    readOnly: true
+  volumes:
+  - name: pull-secret
+    secret:
+      secretName: registry-pull-credentials
 prowjob_default_entries:
 - cluster: '*'
   config: