Fix the CI pipeline for the latest PyTorch release. (microsoft#759)

Author: wenbingl

test/test_processing.py

@@ -92,17 +92,17 @@ def test_gpt2_preprocessing(self):
             merges_file=util.get_test_data_file("data", "gpt2.merges.txt"),
         )
         inputs = tok.forward(test_sentence)
-        pnp.export(tok, test_sentence, opset_version=12, output_path="temp_tok2.onnx")
+        pnp.export(tok, test_sentence, opset_version=14, output_path="temp_tok2.onnx")
 
         with open("temp_gpt2lmh.onnx", "wb") as f:
             torch.onnx.export(
-                gpt2_m, inputs, f, opset_version=12, do_constant_folding=False
+                gpt2_m, inputs, f, opset_version=14, do_constant_folding=False
             )
-        pnp.export(gpt2_m, *inputs, opset_version=12, do_constant_folding=False)
+        pnp.export(gpt2_m, *inputs, opset_version=14, do_constant_folding=False)
         full_model = pnp.SequentialProcessingModule(tok, gpt2_m)
         expected = full_model.forward(test_sentence)
         model = pnp.export(
-            full_model, test_sentence, opset_version=12, do_constant_folding=False
+            full_model, test_sentence, opset_version=14, do_constant_folding=False
         )
         mfunc = OrtPyFunction.from_model(model)
         actuals = mfunc(test_sentence)