delete oss references to caffe2.fb

Summary:
clean up following D56017483

Created from CodeHub with https://fburl.com/edit-in-codehub

Differential Revision: D56043391

Author: henrylhtsang

torchrec/distributed/tests/test_infer_hetero_shardings.py

@@ -15,7 +15,6 @@
 import hypothesis.strategies as st
 
 import torch
-from caffe2.torch.fb.model_transform.splitting.split_dispatcher import SplitDispatchMode
 from hypothesis import given, settings
 from torchrec import EmbeddingBagConfig, EmbeddingCollection, EmbeddingConfig
 from torchrec.distributed.embedding_types import ShardingType