Add guidou@ to chrome/browser/media/webrtc/OWNERS

Change-Id: Ie6e60da92860bc8fdee7e10a2e90b563ea7bec7e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1632242Reviewed-by: Tommi <tommi@chromium.org>
Commit-Queue: Tommi <tommi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663833}

chrome/browser/media/webrtc/OWNERS

 sergeyu@chromium.org
 tommi@chromium.org
+guidou@chromium.org
 
 # For WebRTC desktop capturer related changes only
 braveyao@chromium.org