Skip `test_contrastive_generate` for `TFXLNet` (#25574)

* fix

* fix

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

tests/models/xlnet/test_modeling_tf_xlnet.py

@@ -365,6 +365,12 @@ class TFXLNetModelTest(TFModelTesterMixin, PipelineTesterMixin, unittest.TestCas
     test_head_masking = False
     test_onnx = False
 
+    # Note that `TFXLNetModelTest` is not a subclass of `GenerationTesterMixin`, so no contrastive generation tests
+    # from there is run against `TFXLNetModel`.
+    @unittest.skip("XLNet has special cache mechanism and is currently not working with contrastive generation")
+    def test_xla_generate_contrastive(self):
+        super().test_xla_generate_contrastive()
+
     # TODO: Fix the failed tests
     def is_pipeline_test_to_skip(
         self, pipeline_test_casse_name, config_class, model_architecture, tokenizer_name, processor_name