[snapshot] update OWNERS file.

R=jgruber@chromium.org

Change-Id: I67b296c97091b4bfa3864f5187cf3e7e4d452961
Reviewed-on: https://chromium-review.googlesource.com/604800Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47223}

src/snapshot/OWNERS

 set noparent
 
+jgruber@chromium.org
 verwaest@chromium.org
-vogelheim@chromium.org
 yangguo@chromium.org
 
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