read-only update UX: confusing "Update blocked" pop-up

This is a clone of issue OCPBUGS-4700. The following is the description of the original issue:
—
Description of problem:

In at least 4.12.0-rc.0, a user with read-only access to ClusterVersion can see an "Update blocked" pop-up talking about "...alert above the visualization...".  It is referencing a banner about "This cluster should not be updated to the next minor version...", but that banner is not displayed because hasPermissionsToUpdate is false, so canPerformUpgrade is false.

Version-Release number of selected component (if applicable):

4.12.0-rc.0. Likely more. I haven't traced it out.

How reproducible:

Always.

Steps to Reproduce:

1. Install 4.12.0-rc.0
2. Create a user with cluster-wide read-only permissions. For me, it's via binding to a sudoer ClusterRole. I'm not sure where that ClusterRole comes from, but it's:

$ oc get -o yaml clusterrole sudoer
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
  creationTimestamp: "2020-05-21T19:39:09Z"
  name: sudoer
  resourceVersion: "7715"
  uid: 28eb2ffa-dccd-47e8-a2d5-6a95e0e8b1e9
rules:
- apiGroups:
  - ""
  - user.openshift.io
  resourceNames:
  - system:admin
  resources:
  - systemusers
  - users
  verbs:
  - impersonate
- apiGroups:
  - ""
  - user.openshift.io
  resourceNames:
  - system:masters
  resources:
  - groups
  - systemgroups
  verbs:
  - impersonate

3. View /settings/cluster

Actual results:

See the "Update blocked" pop-up talking about "...alert above the visualization...".

Expected results:

Something more internally consistent. E.g. having the referenced banner "...alert above the visualization..." show up, or not having the "Update blocked" pop-up reference the non-existent banner.