Update class_ir.py

Author: BobTheBuidler

mypyc/ir/class_ir.py

@@ -347,7 +347,7 @@ def subclasses(self) -> set[ClassIR] | None:
         for child in self.children:
             if child.allow_interpreted_subclasses:
                 return None
-            if not (child.is_ext_class or child.is_final):
+            if not (child.is_ext_class or child.is_final_class):
                 return None
             if child.children:
                 child_subs = child.subclasses()