Remove backwards compatible AppRTC download location. TBR=thakis@chromium.org Bug: None Change-Id: I347b30ff1f6b17b94905e10254a4532ec2469109 Reviewed-on: https://webrtc-review.googlesource.com/c/webrtc.DEPS/+/151480 Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>