Update test_dynamic_cache_exportability_multiple_run (failing on torch 2.10 nightly) (#42212)

fix

Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>

Author: ydshieh

tests/utils/test_cache_utils.py

@@ -628,7 +628,7 @@ def test_dynamic_cache_exportability_multiple_run(self):
         past_key_values = res.past_key_values
 
         shapes = torch.export.ShapesCollection()
-        dyn = torch.export.Dim("seq", max=512)
+        dyn = torch.export.Dim.DYNAMIC(max=512)
 
         for ix in range(len(past_key_values)):
             shapes[past_key_values.layers[ix].keys] = (None, None, dyn, None)