Exclude export code path in _use_segment_sum_csr (#3282)

Summary:
Pull Request resolved: #3282

Similar to pt2 compilation path, export path will also not work without concrete stride values.

Reviewed By: angelayi

Differential Revision: D80217808

fbshipit-source-id: 00a21de8332e8106bb91421a41fdd2be622262a2

Author: malaybag

torchrec/sparse/jagged_tensor.py

@@ -1130,7 +1130,7 @@ def _use_segment_sum_csr(stride_per_key: List[int]) -> bool:
     per segment that match performance between the kernel and PyTorch solution, to
     determine the threshold of when to use `segment_sum_csr`.
     """
-    if is_torchdynamo_compiling():
+    if is_pt2_compiling():
         # dynamo symbolic shapes can not pass this condition without concrete stride values
         return False