Ensure Projects::ApproversController inherits from Projects::ApplicationController

Fix gitlab-org/gitlab-ce#14503.

app/controllers/projects/approvers_controller.rb

-class Projects::ApproversController < ApplicationController
+class Projects::ApproversController < Projects::ApplicationController
   def destroy
     if params[:merge_request_id]
       authorize_create_merge_request!
@@ -8,7 +8,7 @@ def destroy
       authorize_admin_project!
       project.approvers.find(params[:id]).destroy
     end
-  
+
     redirect_back_or_default(default: { action: 'index' })
   end
 end