Update c/b/c/arc/input_method_manager/OWNERS

I'm not really working on the IME stuff these days.

BUG=None
TEST=None

Change-Id: I37ac476be426d9f5e5b53ef819989af9976732fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1725289Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Commit-Queue: Yusuke Sato <yusukes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682153}

chrome/browser/chromeos/arc/input_method_manager/OWNERS

+tetsui@chromium.org
 yhanada@chromium.org
-yusukes@chromium.org