Remove channel num check

这个assert是不必要的，因为接下来马上就to mono了
这个assert会不必要的导致在一些测试集上失败，例如 mmau-test，因为这里的音频是6声道的。这本来可以被正确处理，但被assert干掉了。

processor_omni.py

@@ -255,7 +255,7 @@ class OmniAudioProcessor:
 
     def load_audio_waveform(self, uri, return_tensors=True, do_normalize=False):
         metadata = torchaudio.info(uri)  # sample_rate, num_frames, num_channels, bits_per_sample, encoding=PCM_S
-        assert(metadata.num_channels <= 2), "acoustic file with {} channels.".format(metadata.num_channels)  # whisper only accept mono channel audio
+        # assert(metadata.num_channels <= 2), "acoustic file with {} channels.".format(metadata.num_channels)  # whisper only accept mono channel audio
         waveform_tensor, _ = torchaudio.load(uri, normalize=True)
         if self.config.sampling_rate != metadata.sample_rate:
             waveform_tensor = torchaudio.functional.resample(waveform_tensor, metadata.sample_rate, self.config.sampling_rate, lowpass_filter_width=128)