io_uring: remove extra TIF_NOTIFY_SIGNAL check

io_run_task_work() accounts for TIF_NOTIFY_SIGNAL, so no need to have an
second check in io_run_task_work_sig().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/52ce41a592ad904511697f432141e5690fd4b968.1656153285.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>