fix: show pointer only if section is collapsible (backport #23462)

[mergify]

This is an automatic backport of pull request #23462 done by Mergify.
Cherry-pick of 0cd7ee0 has failed:

On branch mergify/bp/version-13-hotfix/pr-23462
Your branch is up to date with 'origin/version-13-hotfix'.

You are currently cherry-picking commit 0cd7ee091f.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   frappe/public/scss/desk/form.scss

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   frappe/public/js/frappe/form/section.js

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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