Remove speex support, it is obsoleted by opus

As mentioned by upstream, Xiph.Org [0]:
> The Speex codec has been obsoleted by Opus. It will continue to be
> available, but since Opus is better than Speex in all aspects,
> users are encouraged to switch.

[0] http://www.speex.org/

platform/javascript/detect.py

@@ -34,7 +34,6 @@ def get_flags():
 		('musepack', 'no'),
 		('squirrel', 'no'),
 		('squish', 'no'),
-		('speex', 'no'),
 		('old_scenes', 'no'),
 		('etc1', 'no'),
 #		('default_gui_theme', 'no'),