Remove deprecated prototype alias (#2583)

Summary:
CTC decoder and StreamReader are now in the main library.
This commit removes their aliases in `torchaudio.prototypes`

Pull Request resolved: https://github.com/pytorch/audio/pull/2583

Reviewed By: mthrok

Differential Revision: D38189314

fbshipit-source-id: c62209f2ad4f7052c6756a537b6fc509064e428c

torchaudio/prototype/ctc_decoder/__init__.py

-def __getattr__(name: str):
-    if name in ["ctc_decoder", "lexicon_decoder"]:
-        import warnings
-
-        from torchaudio.models.decoder import ctc_decoder
-
-        warnings.warn(
-            f"{__name__}.{name} has been moved to torchaudio.models.decoder.ctc_decoder",
-            DeprecationWarning,
-        )
-
-        if name == "lexicon_decoder":
-            global lexicon_decoder
-            lexicon_decoder = ctc_decoder
-            return lexicon_decoder
-        else:
-            return ctc_decoder
-    elif name == "download_pretrained_files":
-        import warnings
-
-        from torchaudio.models.decoder import download_pretrained_files
-
-        return download_pretrained_files
-
-    raise AttributeError(f"module {__name__} has no attribute {name}")
-
-
-def __dir__():
-    return ["ctc_decoder", "lexicon_decoder", "download_pretrained_files"]

torchaudio/prototype/io/__init__.py

-def __getattr__(name: str):
-    if name == "Streamer":
-        import warnings
-
-        from torchaudio.io import StreamReader
-
-        warnings.warn(
-            f"{__name__}.{name} has been moved to torchaudio.io.StreamReader. Please use torchaudio.io.StreamReader",
-            DeprecationWarning,
-        )
-
-        global Streamer
-        Streamer = StreamReader
-        return Streamer
-    raise AttributeError(f"module {__name__} has no attribute {name}")
-
-
-def __dir__():
-    return ["Streamer"]