Merge branch '55948-help-text-formatting-wiki' into 'master'

Format extra help page text like wiki

Closes #55948

See merge request gitlab-org/gitlab-ce!26782

app/views/help/index.html.haml

 %div
 - if Gitlab::CurrentSettings.help_page_text.present?
+  .prepend-top-default.md
     = markdown_field(Gitlab::CurrentSettings.current_application_settings, :help_page_text)
   %hr
 

changelogs/unreleased/55948-help-text-formatting-wiki.yml

+---
+title: Format extra help page text like wiki
+merge_request: 26782
+author: Bastian Blank
+type: fixed