Remove remaining samples (AppRTC) since moved to Github

In r5871 the samples directory was removed since they've now
moved to GitHub at https://github.com/GoogleChrome/webrtc

AppRTC needed to be kept in here (restored in r5873) since
automated tests in Chromium pulled AppRTC.
Now that a Chromium mirror has been setup for the GitHub repo
and that the automated tests have been updated, we can remove
this once and for all.

BUG=chromium:362483
TEST=None, but the automated tests have been verified syncing
the new location.

R=tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/19639004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6342 4adac7df-926f-26a2-2b94-8c16560cd09d