[TaskScheduler] Remove unused base/task_scheduler/OWNERS

Bug: 870426
Change-Id: I7f9b5eac1ec4146df43492fe37b1607655c1ca42
Reviewed-on: https://chromium-review.googlesource.com/1163308Reviewed-by: Robert Liao <robliao@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581231}

base/task_scheduler/OWNERS

-# TODO(gab): Remove this file from this now empty directory after
-# base/test/OWNERS is updated on the server to no longer refer to it...
-# https://crbug.com/870426
-
-fdoray@chromium.org
-gab@chromium.org
-robliao@chromium.org
-
-# TEAM: scheduler-dev@chromium.org
-# COMPONENT: Internals>TaskScheduler