Do not allow adding new API users outside of registrar details view

This feature is not needed.

app/views/admin/api_users/index.haml

@@ -1,5 +1,3 @@
-- content_for :actions do
-  = link_to(t('.new_btn'), new_admin_api_user_path, class: 'btn btn-primary')
 = render 'shared/title', name: t('.title')
 
 .row

config/locales/admin/api_users.en.yml

@@ -2,7 +2,6 @@ en:
   admin:
     api_users:
       index:
-        new_btn: New API user
         title: API users
         active: Active
 

config/routes.rb

@@ -270,7 +270,7 @@ Rails.application.routes.draw do
     end
 
     resources :admin_users
-    resources :api_users do
+    resources :api_users, except: %i[new] do
       resources :certificates do
         member do
           post 'sign'