Fix breadcrumb for security page

ee/app/views/layouts/instance_security.html.haml

 - page_title _('Security')
-- header_title _('Security')
+- header_title _('Security'), security_root_path
 - nav 'security'
 - @left_sidebar = true
 

ee/changelogs/unreleased/djadmin-fix-breadcrumb.yml

+---
+title: Fix breadcrumb for security dashboard
+merge_request: 40486
+author:
+type: fixed