io_tester: Remove unused code
io_tester: Remove unused code

The class_data::describe_class() is no longer used

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

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