In 1c42fd93 the ipcm identifier was
added in order to demux additional raw audio from Sony MP4 files.
Unfortunately, it was not noticed that this same list is utilized
for muxing as well, thus causing ipcm to get preferred compared
to the identifier officially specified in QTFF documentation.

This fixes the order of preference for 24bit PCM, where ipcm is
still allowed, but in24 is the first match - thus being preferred.

Fixes fate-acodec-pcm-s24be.