style: Fix rstcheck's "Title underline too short."

reference/library-reference.rst

@@ -228,7 +228,7 @@ Returns the most likely transcription if ``show_all`` is false (the default). Ot
 Raises a ``speech_recognition.UnknownValueError`` exception if the speech is unintelligible. Raises a ``speech_recognition.RequestError`` exception if the speech recognition operation failed, if the key isn't valid, or if there is no internet connection.
 
 ``recognizer_instance.recognize_google_cloud(audio_data: AudioData, credentials_json: Union[str, None] = None, language: str = "en-US", preferred_phrases: Union[Iterable[str], None] = None, show_all: bool = False, **api_params) -> Union[str, Dict[str, Any]]``
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 Performs speech recognition on ``audio_data`` (an ``AudioData`` instance), using the Google Cloud Speech API.