Fixed %placeholder style-lint error for projects.scss

9:3 Expected a placeholder selector (e.g. %placeholder) to be used in
@extend

ee/app/assets/javascripts/protected_environments/protected_environment_edit_list.js

@@ -5,7 +5,7 @@ import ProtectedEnvironmentEdit from './protected_environment_edit';
 
 export default class ProtectedEnvironmentEditList {
   constructor() {
-    this.$wrap = $('.protected-environments-list');
+    this.$wrap = $('.protected-branches-list');
     this.initEditForm();
   }
 

ee/app/assets/stylesheets/pages/projects.scss

@@ -5,10 +5,6 @@
   }
 }
 
-.protected-environments-list {
-  @extend .protected-branches-list;
-}
-
 .project-mirror-settings {
   .fingerprint-verified {
     color: $green-500;

ee/app/views/projects/protected_environments/_environments_list.html.haml

-.protected-environments-list.js-protected-environments-list
+.protected-branches-list.js-protected-environments-list
   - if @protected_environments.empty?
     %p.settings-message.text-center
       = s_('ProtectedEnvironment|There are currently no protected environments, protect an environment with the form above.')

ee/spec/features/projects/settings/protected_environments_spec.rb

@@ -44,7 +44,7 @@ describe 'Protected Environments' do
     end
 
     it 'allows seeing a list of protected environments' do
-      within('.protected-environments-list') do
+      within('.protected-branches-list') do
         expect(page).to have_content('production')
         expect(page).to have_content('removed environment')
       end
@@ -60,31 +60,31 @@ describe 'Protected Environments' do
 
       wait_for_requests
 
-      within('.protected-environments-list') do
+      within('.protected-branches-list') do
         expect(page).to have_content('staging')
       end
     end
 
     it 'allows updating access to a protected environment', :js, :quarantine do
-      within('.protected-environments-list tr', text: 'production') do
+      within('.protected-branches-list tr', text: 'production') do
         set_allowed_to_deploy('Developers + Maintainers')
       end
 
       visit project_settings_ci_cd_path(project)
 
-      within('.protected-environments-list') do
+      within('.protected-branches-list') do
         expect(page).to have_content('1 role, 1 user')
       end
     end
 
     it 'allows unprotecting an environment', :js do
-      within('.protected-environments-list tr', text: 'production') do
+      within('.protected-branches-list tr', text: 'production') do
         accept_alert { click_on('Unprotect') }
       end
 
       wait_for_requests
 
-      within('.protected-environments-list') do
+      within('.protected-branches-list') do
         expect(page).not_to have_content('production')
       end
     end