Update histograms.xml so that the ."HandshakeConfirmed" suffix applies
to the "Google" variants of the QUIC connection close error histograms.

Change-Id: I156dd9cff57fff298095ee692cf8da9f1a5a955d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1585175
Reviewed-by: Nik Bhagat <nikunjb@chromium.org>
Commit-Queue: Ryan Hamilton <rch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654641}