[omnibox] Add manukh and orinj to OWNERS.

Both are committers, have been on the omnibox team for over a year, and
have demonstrated good knowledge and judgement in code reviews.

Change-Id: I88c1aa50cff969a4afb6a958e5ac2c01b69a385f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1765658Reviewed-by: Tommy Li <tommycli@chromium.org>
Commit-Queue: Justin Donnelly <jdonnelly@chromium.org>
Cr-Commit-Position: refs/heads/master@{#689612}

components/omnibox/OWNERS

 jdonnelly@chromium.org
 krb@chromium.org
+manukh@chromium.org
 mpearson@chromium.org
+orinj@chromium.org
 tommycli@chromium.org
 
 # COMPONENT: UI>Browser>Omnibox