Because of the patch that removed the "user sources list" in libobs
(70fec7ae), obs_enum_sources will now enumerate the global audio
sources, where it didn't before.  In the advanced audio properties
dialog, before the patch I had to use code to manually include them, but
I neglected to remove that code when I made that patch, so it would
cause them to be added more than once.  This just removes that code.