Add ipc/mojo/OWNERS

Don't bother IPC owners with mojo changes.

TEST=none
BUG=none
R=darin@chromium.org,jam@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/451073002

Cr-Commit-Position: refs/heads/master@{#288395}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288395 0039d316-1c4b-4281-b951-d872f2087c98

ipc/mojo/OWNERS

+morrita@chromium.org
+viettrungluu@chromium.org
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