Changes the video payload type allocation to use the lower dynamic payload type range [35,65] described in https://www.iana.org/assignments/rtp-parameters/rtp-parameters.xhtml#rtp-parameters-1 for new codecs such as FlexFEC. BUG=webrtc:12194 Change-Id: I71782199074e0fc94fa6aa8c36afeb68221a2839 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/195822 Commit-Queue: Harald Alvestrand <hta@webrtc.org> Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org> Reviewed-by: Harald Alvestrand <hta@webrtc.org> Cr-Commit-Position: refs/heads/master@{#32799}