Remove jgraettinger@chromium.org as a net owner

as he no longer works on Chromium.

Also transfer ownership of the histogram he owned.

BUG=NONE
NOTRY=true

Review URL: https://codereview.chromium.org/617573002

Cr-Commit-Position: refs/heads/master@{#297425}

net/OWNERS

@@ -5,7 +5,6 @@ davidben@chromium.org
 eroman@chromium.org
 gavinp@chromium.org
 jar@chromium.org
-jgraettinger@chromium.org
 mattm@chromium.org
 mef@chromium.org
 mmenke@chromium.org

tools/metrics/histograms/histograms.xml

@@ -17599,7 +17599,7 @@ Therefore, the affected-histogram name has to have at least one dot in it.
 </histogram>
 
 <histogram name="Net.SpdyHpackEncodedCharacterFrequency" units="ASCII codes">
-  <owner>jgraettinger@chromium.org</owner>
+  <owner>bnc@chromium.org</owner>
   <summary>
     Frequencies of characters observed in request and response headers.
     Temporarily being collected to inform the construction of an optimized