Starting new audio codecs from the top of the lower range
reduces collisions with video codecs which are assigned from
the bottom of the lower range
BUG=webrtc:11640
Change-Id: If6d2b849b8e1de777a1d4352df533e4f1845fde9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/220022
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34166}