Add tby@ as histograms.xml OWNER for chrome knowledge metrics.

Change-Id: I15a437a11922af307a7cbf800b01529131429dea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2064229Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Tony Yeoman <tby@chromium.org>
Cr-Commit-Position: refs/heads/master@{#743313}

tools/metrics/histograms/OWNERS

@@ -10,6 +10,7 @@ per-file histograms.xml=csharrison@chromium.org
 per-file histograms.xml=cthomp@chromium.org  # For security-related metrics only.
 per-file histograms.xml=schenney@chromium.org
 per-file histograms.xml=tbansal@chromium.org
+per-file histograms.xml=tby@chromium.org # For chrome knowledge team metrics only.
 
 per-file histograms.xml=set noparent