Update chrome/renderer/supervised_user/OWNERS to refer to browser version

There's no reason to have different owners for the supervised users code
in the renderer. In practice, the renderer OWNERS file was just an
outdated copy of the browser one.

Bug: none
Change-Id: I81d74c3781ad218e2b30bd30a03e9bf4af22be1b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1865322
Auto-Submit: Marc Treib <treib@chromium.org>
Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Commit-Queue: Michael Giuffrida <michaelpg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707103}

chrome/renderer/supervised_user/OWNERS

-escordeiro@chromium.org
-menegola@chromium.org
-pam@chromium.org
-treib@chromium.org
+file://chrome/browser/supervised_user/OWNERS
 
 # COMPONENT: Services>SupervisedUser