io_queue: Deprecate max-io-requests option
io_queue: Deprecate max-io-requests option

The configured by it io_queue::_capacity is deprecated long ago.
The same should be done for the option itself.

Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@scylladb.com>

cloudius-systems/seastar,syuu1228/seastar,cloudius-systems/seastar,scylladb/seastar,syuu1228/seastar,cloudius-systems/seastar,syuu1228/seastar,scylladb/seastar,scylladb/seastar,avikivity/seastar,avikivity/seastar,avikivity/seastar