disable contextlib in PT2 train pipeline (#2730)

Summary:

    Pull Request resolved: #2596

# context
* more details in the [post](https://fb.workplace.com/groups/1075192433118967/permalink/1587079018596970/)
* disable contextlib with PT2

Differential Revision: D68480678

torchrec/distributed/train_pipeline/train_pipelines.py

@@ -269,6 +269,7 @@ def progress(self, dataloader_iter: Iterator[In]) -> Out:
 
                 # Mandatory dynamo configuration for Torchrec PT2 compilation
                 torch._dynamo.config.capture_scalar_outputs = True
+                torch._dynamo.config.enable_trace_contextlib = False
                 torch._dynamo.config.capture_dynamic_output_shape_ops = True
                 torch._dynamo.config.force_unspec_int_unbacked_size_like_on_torchrec_kjt = (
                     True