Replace reinauer with kitching in OWNERS file

BUG=None
TEST=None

Change-Id: I56020f2559874a66f95813bf28be36854e26b7b8
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/bootstub/+/2567034
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Stefan Reinauer <reinauer@chromium.org>
Commit-Queue: Furquan Shaikh <furquan@chromium.org>
Tested-by: Furquan Shaikh <furquan@chromium.org>