Search Engines: Add Omnibox team to search_engines component OWNERS

pkasting@ is already in the omnibox component OWNERS file, so he will
remain an OWNER of search_engines after this CL.

chrome/browser/search_engines includes the below OWNERS file, so it
doesn't directly need updating.

I'm updating chrome/browser/ui/search_engines as well, as our team
recently added code to the SearchEngineTabHelper to auto-update the
default search provider favicons as the user browses.

Bug: NONE
Change-Id: Ib26716fb8ce00b3a166769611e87c4c80273ecba
Reviewed-on: https://chromium-review.googlesource.com/c/1329892Reviewed-by: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Commit-Queue: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607275}

chrome/browser/ui/search_engines/OWNERS

-pkasting@chromium.org
+file://components/search_engines/OWNERS
+
 sky@chromium.org
 
 # COMPONENT: UI>Browser>Search

components/search_engines/OWNERS

-pkasting@chromium.org
+file://components/omnibox/OWNERS
+
 vasilii@chromium.org
 
 # COMPONENT: UI>Browser>Search