[dynamo] Function => FunctionCtx for placeholder obj (#120577)

Pull Request resolved: https://github.com/pytorch/pytorch/pull/120577
Approved by: https://github.com/yanboliang
diff --git a/torch/_dynamo/side_effects.py b/torch/_dynamo/side_effects.py
index 67cdb8f..1e331ac 100644
--- a/torch/_dynamo/side_effects.py
+++ b/torch/_dynamo/side_effects.py
@@ -242,7 +242,7 @@
         options,
     ):
         if user_cls is torch.autograd.function.FunctionCtx:
-            obj = torch.autograd.Function()
+            obj = torch.autograd.function.FunctionCtx()
         elif issubclass(user_cls, torch.nn.Module):
             obj = nn_module_new(user_cls)
         else: