Fixes the default branch link under pipeline subscriptions in CI/CD settings

changelogs/unreleased/docs-fix_default_branches_link.yml

+---
+title: Fixed default-branch link under Pipeline Subscription settings
+merge_request: 24834
+author: James Johnson
+type: fixed

ee/app/views/projects/settings/ci_cd/_pipeline_subscriptions.html.haml

@@ -9,7 +9,7 @@
     %p
       = _("Set up pipeline subscriptions for this project.")
     %p
-      - default_branch_docs = link_to(_("default branch"), help_page_path('user/project/repository/branches', anchor: 'default-branch'))
+      - default_branch_docs = link_to(_("default branch"), help_page_path('user/project/repository/branches/index.md', anchor: 'default-branch'))
       = _("Subscriptions allow successfully completed pipelines on the %{default_branch_docs} of the subscribed project to trigger a new pipeline on the default branch of this project.").html_safe % { default_branch_docs: default_branch_docs }
     %p
       = _("There is a limit of 100 subscriptions from or to a project.")