Prophetnet batch dimension inversion fix (#21870)

* decoder forward pass is working

* no model has forward pass returning attentions

* decoder ngram changed to not mix batch size

* current basic forward pass returns identical result

* passed test_model attentions

* passed test_encoder_decoder_model_generate

* passed test_headmasking

* removed old block

* removed comments bug/fixme

* removed bug comments

* applied styling

* applied fix-copies

* applied ngram forward comments

* corrected dimension notation

* applied styling and comment fixes

* changed asserts for raise ValueError

* changed question gen test

* updated hidden_states integration test

* applied styling

tests/models/prophetnet/test_modeling_prophetnet.py

@@ -1206,7 +1206,7 @@ class ProphetNetModelIntegrationTest(unittest.TestCase):
         expected_shape = torch.Size((1, 12, 30522))
         self.assertEqual(output_predited_logits.shape, expected_shape)
         expected_slice = torch.tensor(
-            [[[-7.6213, -7.9008, -7.9979], [-7.6834, -7.8467, -8.2187], [-7.5326, -7.4762, -8.1914]]]
+            [[[-7.7729, -8.0343, -8.26001], [-7.74213, -7.8629, -8.6000], [-7.7328, -7.8269, -8.5264]]]
         ).to(torch_device)
         #        self.assertTrue(torch.allclose(output_predited_logits[:, :3, :3], expected_slice, atol=1e-4))
         assert torch.allclose(output_predited_logits[:, :3, :3], expected_slice, atol=1e-4)
@@ -1306,7 +1306,7 @@ class ProphetNetModelIntegrationTest(unittest.TestCase):
         EXPECTED_QUESTIONS = [
             "along with paul allen, who founded microsoft?",
             "what year was microsoft founded?",
-            "on what date was microsoft founded?",
+            "when was microsoft founded?",
         ]
 
         self.assertListEqual(