Delete last file in neteq4 folder

The .isolate file can now be safely removed, since issue 3462 is
resolved.

BUG=2996
R=kjellander@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/16659004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6388 4adac7df-926f-26a2-2b94-8c16560cd09d