Remove i420_video_frame.h from common_video.gyp

i420_video_frame.h was removed in
https://webrtc-codereview.appspot.com/46819004/
but common_video.gyp was not updated with this change.

BUG=N/A
TBR=tfarina@chromium.org

Review URL: https://webrtc-codereview.appspot.com/51569004

Cr-Commit-Position: refs/heads/master@{#8974}
1 file changed