smp: work_item: remove redundant try/catch
smp: work_item: remove redundant try/catch

futurator and with_scheduling_group are noexcept, so the try/catch is
redundant. Remove it.

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