Remove the now defunct menu items for Drupal 11 sites
Routes to add a theme or module where removed in #3417136: Remove adding an extension via a URL. This code is now live with Drupal 11 and causes a whitepage when navigating to the /admin/structure/menu/manage/admin page.
This affects menu items added by the ExtraLinks class:
update.module_install
update.theme_install
Signed-off-by: Wong Hoi Sing Edison hswong3i@pantarei-design.com
Closes #3474908