Re-add the :push_code_to_protected_branches permission

This was removed in gitlab-org/gitlab-ce!11000.
Signed-off-by: Rémy Coutable <remy@rymai.me>

app/policies/project_policy.rb

@@ -110,6 +110,7 @@ class ProjectPolicy < BasePolicy
   end
 
   def master_access!
+    can! :push_code_to_protected_branches
     can! :delete_protected_branch
     can! :update_project_snippet
     can! :update_environment
@@ -188,6 +189,7 @@ class ProjectPolicy < BasePolicy
   def archived_access!
     cannot! :create_merge_request
     cannot! :push_code
+    cannot! :push_code_to_protected_branches
     cannot! :delete_protected_branch
     cannot! :update_merge_request
     cannot! :admin_merge_request
@@ -236,6 +238,7 @@ class ProjectPolicy < BasePolicy
 
     unless repository_enabled
       cannot! :push_code
+      cannot! :push_code_to_protected_branches
       cannot! :delete_protected_branch
       cannot! :download_code
       cannot! :fork_project

spec/policies/project_policy_spec.rb

@@ -44,7 +44,8 @@ describe ProjectPolicy, models: true do
 
   let(:master_permissions) do
     %i[
-      delete_protected_branch update_project_snippet update_environment
+      push_code_to_protected_branches delete_protected_branch
+      update_project_snippet update_environment
       update_deployment admin_milestone admin_project_snippet
       admin_project_member admin_note admin_wiki admin_project
       admin_commit_status admin_build admin_container_image