block: remove Documentation/block/as-iosched.txt

Commit 492af6350a5ccf087e4964104a276ed358811458 removed
the AS IO scheduler, so remove its documentation too.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2 files changed