speechdispatcherfactory: Do not set voice name when it is the default
speechdispatcherfactory: Do not set voice name when it is the default

self._default_voice_name (i.e. "<synth_name> default voice") is just
the end-user (translated, even!) label for asking for the default
speech-dispatcher voice. We should not be asking speech-dispatcher a voice
with that name, and just rely on the selection from the locale.

GNOME/orca,GNOME/orca,GNOME/orca,GNOME/orca