remove the script-message commands that older mpv version don't support

https://github.com/ankitects/anki/pull/671#issuecomment-647798343

qt/aqt/sound.py

@@ -338,7 +338,6 @@ class MpvManager(MPV, SoundOrVideoPlayer):
         assert isinstance(tag, SoundOrVideoTag)
         self._on_done = on_done
         path = os.path.join(os.getcwd(), tag.filename)
-        self.command("script-message", "osc-visibility", "never", "no-osd")
         self.command("loadfile", path, "append-play")
         gui_hooks.av_player_did_begin_playing(self, tag)
 
@@ -355,9 +354,6 @@ class MpvManager(MPV, SoundOrVideoPlayer):
         if val and self._on_done:
             self._on_done()
 
-    def on_start_file(self) -> None:
-        self.command("script-message", "osc-visibility", "auto", "no-osd")
-
     def shutdown(self) -> None:
         self.close()