Remove ivinnichenko from webrtc/test/OWNERS

Apparently, We're doing a poor job of cleaning out
really old OWNERS.

R=phoglund@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/20669004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6447 4adac7df-926f-26a2-2b94-8c16560cd09d