Removes 'experimental' label from cluster views

What does this MR do?

As part of https://gitlab.com/gitlab-org/gitlab-ce/issues/51716, we need to remove 'experimental' labels from cluster views (show and form), as well as the prompt about cluster configuration, since it won't apply.

These changes were originally introduced (and are going to be used) on https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/22011/, but we're trying to reduce the size of that MR as it's too big to review with confidence.

What are the relevant issue numbers?

Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/51716

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [-] Documentation created/updated
• [-] Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• [-] Link to e2e tests MR added if this MR has ~"Requires e2 tests" label. See the Test Planning Process.