Fix message

Author: mthrok

torchaudio/functional.py

@@ -126,7 +126,7 @@ def istft(
         Tensor: Least squares estimation of the original signal of size (..., signal_length)
     """
     warnings.warn(
-        'istft has been moved to PyTorch and will be deprecated, please use torch.istft instead.')
+        'istft has been moved to PyTorch and will be removed, please use torch.istft instead.')
     warnings.warn(
         '`pad_mode` for istft function is deprecated and will be removed. '
         'It was introduced accidentally and never used. '