Improve the style of the objc wrapper for PeerConnectionInterface::SetBitrate.

BUG=webrtc:7395

Review-Url: https://codereview.webrtc.org/3011013002
Cr-Original-Commit-Position: refs/heads/master@{#19697}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 8b476173d897c8e88330de683f9f9e9c81e76589
3 files changed