Fix clusters description text collapsing away on page-load

What does this MR do?

EE MR, https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3264

• Fix clusters description text collapsing away on page-load

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Description/help text in "Enable cluster integration" settings section collapses away on page load

https://gitlab.com/gitlab-org/gitlab-ce/issues/39771

Caused by a recent change in how/where the .expanded class is handled, https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13363

Does this MR meet the acceptance criteria?

• Tests added for this feature/bug
• Review
  • Has been reviewed by Frontend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #39771 (closed)