Rename (packets|bytes)_dropped to (packets|bytes)_discarded_no_receiver in PC level framework based tests to make it more clear for metric means. Bug: None Change-Id: I8d36f5d03399ad40cd367bb65410ff97a0616d4e Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/212611 Commit-Queue: Artem Titov <titovartem@webrtc.org> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Cr-Commit-Position: refs/heads/master@{#33513}