Remove suppressions for VideoFrame::Validate.

BUG=3789
R=sprang@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/24549004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7136 4adac7df-926f-26a2-2b94-8c16560cd09d