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}