Merge branch 'move-off-backstage' into 'master'

Mention ~"feature::maintenance" over ~backstage

See merge request gitlab-org/omnibus-gitlab!4585

scripts/support/specs/Dangerfile

 NO_NEW_SPEC_MESSAGE = <<~MSG.freeze
 You've made some changes in the cookbooks, but didn't add any tests.
 That's OK as long as you're refactoring existing code,
-but please consider adding the ~backstage label in that case.
+but please consider adding the ~"feature::maintenance" label in that case.
 MSG
 has_app_changes = !git.modified_files.grep(%r{\A(files|lib)/}).empty?

scripts/support/template/Dangerfile

@@ -49,7 +49,7 @@ You've made some changes at the locations which contain user facing configuratio
 That's OK as long as you're refactoring existing code and not adding any new
 configuration. If you are adding new user facing configuration, consider adding
 to gitlab.rb.template located in files/gitlab-config-template/gitlab.rb.template .
-Otherwise, please consider adding the ~backstage label in that case.
+Otherwise, please consider adding the ~"feature::maintenance" label in that case.
 MSG
 warn NO_TEMPLATE_CHANGE_MESSAGE, sticky: false if !git.modified_files.include?('files/gitlab-config-template/gitlab.rb.template') && !configuration_paths_to_review.empty?