danger: Don't override already-set scoped labels

Signed-off-by: Rémy Coutable <remy@rymai.me>

danger/specialization_labels/Dangerfile

@@ -15,8 +15,14 @@ SPECIALIZATIONS = {
 
 labels_to_add = project_helper.changes_by_category.each_with_object([]) do |(category, _changes), memo|
   label = SPECIALIZATIONS[category]
+  next unless label
+  next if gitlab.mr_labels.include?(label)
 
-  memo << label if label && !gitlab.mr_labels.include?(label)
+  # Don't override already-set scoped labels.
+  label_scope = label.split('::')[0...-1].join('::')
+  next if !label_scope.empty? && gitlab.mr_labels.any? { |mr_label| mr_label.start_with?(label_scope) }
+
+  memo << label
 end
 
 project_helper.labels_to_add.concat(labels_to_add) if labels_to_add.any?