Update endpoints to reference feature category as PA

app/controllers/admin/ci/variables_controller.rb

 # frozen_string_literal: true
 class Admin::Ci::VariablesController < Admin::ApplicationController
-  feature_category :continuous_integration
+  feature_category :pipeline_authoring
   def show
     respond_to do |format|

app/controllers/groups/variables_controller.rb

@@ -6,7 +6,7 @@ class VariablesController < Groups::ApplicationController
     skip_cross_project_access_check :show, :update
-    feature_category :continuous_integration
+    feature_category :pipeline_authoring
     def show
       respond_to do |format|

app/controllers/projects/variables_controller.rb

@@ -3,7 +3,7 @@
 class Projects::VariablesController < Projects::ApplicationController
   before_action :authorize_admin_build!
-  feature_category :continuous_integration
+  feature_category :pipeline_authoring
   def show
     respond_to do |format|

ee/lib/api/project_mirror.rb

@@ -2,7 +2,7 @@
 module API
   class ProjectMirror < ::API::Base
-    feature_category :continuous_integration
+    feature_category :pipeline_authoring
     helpers do
       def github_webhook_signature