Add a comment about implementing proper policies for group runner permissions

app/controllers/groups/runners_controller.rb

 class Groups::RunnersController < Groups::ApplicationController
+  # Proper policies should be implemented per
+  # https://gitlab.com/gitlab-org/gitlab-ce/issues/45894
   before_action :authorize_admin_pipeline!
+
   before_action :runner, only: [:edit, :update, :destroy, :pause, :resume, :show]
   def show

app/views/groups/runners/_group_runners.html.haml

@@ -4,6 +4,8 @@
   GitLab Group Runners can execute code for all the projects in this group.
   They can be managed using the #{link_to 'Runners API', help_page_path('api/runners.md')}.
+-# Proper policies should be implemented per
+-# https://gitlab.com/gitlab-org/gitlab-ce/issues/45894
 - if can?(current_user, :admin_pipeline, @group)
   = render partial: 'ci/runner/how_to_setup_runner',
            locals: { registration_token: @group.runners_token, type: 'group' }