Fix onnx export for transformers>=4.45 (#2054)

* fix onnx export for transformers>=4.45

* fix tets

* style

Author: echarlaix

optimum/exporters/onnx/convert.py

@@ -1128,7 +1128,11 @@ def onnx_export_from_model(
 
         if check_if_transformers_greater("4.44.99"):
             misplaced_generation_parameters = model.config._get_non_default_generation_parameters()
-            if isinstance(model, GenerationMixin) and len(misplaced_generation_parameters) > 0:
+            if (
+                isinstance(model, GenerationMixin)
+                and model.can_generate()
+                and len(misplaced_generation_parameters) > 0
+            ):
                 logger.warning(
                     "Moving the following attributes in the config to the generation config: "
                     f"{misplaced_generation_parameters}. You are seeing this warning because you've set "

tests/exporters/onnx/test_exporters_onnx_cli.py

@@ -602,6 +602,7 @@ def test_diffusion(self):
                 check=True,
             )
 
+    @require_sentence_transformers
     def test_sentence_transformers(self):
         with TemporaryDirectory() as tmpdirname:
             subprocess.run(