[Lookalikes] Update DIR_METADATA and OWNERS for Lookalikes

This CL removes OWNERS for lookalikes for
//components/security_interstitials/OWNERS. As the purview of lookalike
owners grows (e.g. crrev.com/c/2628137 ), we should probably manage this
a little more closely. The existing list also included a bunch of folks
who know a lot about security interstitials, but should really chat with
us before they change lookalikes stuff.

It also updates the component for chrome/browser/lookalikes, since we
have something more specific now.

Change-Id: I1ee4fd4fc6d551a458cad36563d1f1ce445ce2b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2630744
Commit-Queue: Mustafa Emre Acer <meacer@chromium.org>
Reviewed-by: Mustafa Emre Acer <meacer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843929}

chrome/browser/lookalikes/DIR_METADATA

 monorail:  {
-  component: "UI>Browser>Interstitials"
+  component: "UI>Browser>LookalikeChecks"
 }

chrome/browser/lookalikes/OWNERS

-file://components/security_interstitials/OWNERS
 jdeblasio@chromium.org
+meacer@chromium.org
+estark@chromium.org