remove unused function _get_unflattened_lengths (#2573)

Summary:
Pull Request resolved: #2573

as title

Reviewed By: PaulZhang12

Differential Revision: D66219413

fbshipit-source-id: 3df475b2f0fd5d5819c75fcbf8f5b84b5b45105a

Author: seanx92

torchrec/modules/utils.py

@@ -48,17 +48,6 @@ def _slice_1d_tensor(tensor: torch.Tensor, start: int, end: int) -> torch.Tensor
     return tensor[start:end]
 
 
-# PLEASE DO NOT USE THIS FUNCTION, THIS FUNCTION IS FOR BACKWARD COMPATIBILITY ONLY
-# USE THE ONE IN torchrec/quant/embedding_modules.py
-# TODO(@shuaoxiong): remove this function after we make sure all models switch to the new reference
-@torch.fx.wrap
-def _get_unflattened_lengths(lengths: torch.Tensor, num_features: int) -> torch.Tensor:
-    """
-    Unflatten lengths tensor from [F * B] to [F, B].
-    """
-    return lengths.view(num_features, -1)
-
-
 def extract_module_or_tensor_callable(
     module_or_callable: Union[
         Callable[[], torch.nn.Module],