Don't show delete build button if build is marked to be kept

[NotMyFault]

The change proposed hides the Delete build '#' button if a build is marked to be kept and shows again if you no longer want to keep the build.

294e094503dbb07743599cedf04894f2.mp4

Proposed changelog entries

• Hide "Delete build '#'" button if "Keep this build forever" is selected.

Proposed upgrade guidelines

N/A

Submitter checklist

• Changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developer, depending on the change) and are in the imperative mood. Examples
  • Fill-in the Proposed changelog entries section only if there are breaking changes or other changes which may require extra steps from users during the upgrade

Desired reviewers

@mention

Maintainer checklist

Before the changes are marked as ready-for-merge:

• There are at least 2 approvals for the pull request and no outstanding requests for change
• Conversations in the pull request are over OR it is explicit that a reviewer does not block the change
• Changelog entries in the PR title and/or Proposed changelog entries are accurate, human-readable, and in the imperative mood
• Proper changelog labels are set so that the changelog can be generated automatically
• If the change needs additional upgrade steps from users, upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the PR title. (example)
• If it would make sense to backport the change to LTS, a Jira issue must exist, be a Bug or Improvement, and be labeled as lts-candidate to be considered (see query).

[MarkEWaite]

Confirmed it is working with interactive testing of a freestyle project

[MarkEWaite]

This PR is now ready for merge. We will merge it after approximately 24 hours if there is no negative feedback.

[daniel-beck]

It's possible that the difference between "lacking Run/Delete" and a build being marked as kept forever may be too subtle now, and cause confusion why this action is unavailable?

At least we still have the build badge as UI showing why a build cannot be deleted (even though that is nowhere visible from any build-related page now), now that the option to view this page is gone.

Is it deliberate to keep the view around?