Revert of RTCInboundRTPStreamStats.qpSum collected. (patchset #4 id:80001 of https://codereview.webrtc.org/2675943002/ )

Reason for revert:
Breaks downstream build.

Original issue's description:
> RTCInboundRTPStreamStats.qpSum collected.
>
> This was previously only collected for local tracks
> (RTCOutboundRTPStreamStats.qpSum).
>
> Spec: https://w3c.github.io/webrtc-stats/#dom-rtcrtpstreamstats-qpsum
>
> This CL also improves some testing in rtcstatscollector_unittest.cc.
> Default and non-default values are tested in the same unittests,
> removing the test that was specific to default-values, which was
> otherwise code duplication.
>
> BUG=webrtc:7065
>
> Review-Url: https://codereview.webrtc.org/2675943002
> Cr-Commit-Position: refs/heads/master@{#16477}
> Committed: https://chromium.googlesource.com/external/webrtc/+/cd195bea5e38a61e73b08f82445560d9136cd9da

TBR=sakal@webrtc.org,hta@webrtc.org,hbos@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:7065

Review-Url: https://codereview.webrtc.org/2687483002 .
Cr-Original-Commit-Position: refs/heads/master@{#16479}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: ed02c6d68f31baed3cfb7656062895a4d1cb7e65
4 files changed