UPSTREAM: signal: kill JOBCTL_TASK_WORK

[ Upstream commit 98b89b64 ]

It's no longer used, get rid of it.

Change-Id: Id14379554f3e1085c63ac4d044618f609ebc2f9f
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit c91ab047)
Bug: 268174392
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>