fix testing_only_docs

Author: simlay

src/ir/objc.rs

@@ -35,6 +35,7 @@ pub struct ObjCInterface {
     /// The list of protocols that this interface conforms to.
     pub conforms_to: Vec<ItemId>,
 
+    /// The list of parents that this interface has.
     pub parent_classes: Vec<ItemId>,
 
     /// List of the methods defined in this interfae