Revert 174684 "Add ager@ to core/OWNERS"

I was too rushed to land the change. I should have waited for a couple of more days
to give folks a chance to comment on the core owner nomination.

> Add ager@ to core/OWNERS
> 
> TBR=eseidel
> NOTRY=true
> 
> Review URL: https://codereview.chromium.org/296853011

TBR=haraken@chromium.org

Review URL: https://codereview.chromium.org/289283022

git-svn-id: svn://svn.chromium.org/blink/trunk@174686 bbb929c8-8fbe-4397-9dbb-9b2b20218538