coreml: fix audio shape in whisper decoder conversion [no ci]

This commit fixes the audio shape in the whisper decoder conversion
script.

The motivation for this is that the  audio shape was incorrect and
was causing the conversion to fail.

Author: danbev

models/convert-whisper-to-coreml.py

@@ -269,10 +269,11 @@ def convert_decoder(hparams, model, quantize=False):
     model.eval()
 
     tokens_shape = (1, 1)
-    audio_shape = (1, hparams.n_audio_state, 1, 1500)
+    audio_shape = (1, hparams.n_audio_ctx, hparams.n_audio_state)
 
     audio_data = torch.randn(audio_shape)
-    token_data = torch.randint(50257, tokens_shape).long()
+    token_data = torch.randint(hparams.n_vocab, tokens_shape).long()
+
     traced_model = torch.jit.trace(model, (token_data, audio_data))
 
     model = ct.convert(