native-stack: Mark tcb::clear_delayed_ack() and tcb::stop_retransmit_timer() noexcept
native-stack: Mark tcb::clear_delayed_ack() and tcb::stop_retransmit_timer() noexcept

These two cancel timers, which is no-throwing operation

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

syuu1228/seastar,syuu1228/seastar,scylladb/seastar,scylladb/seastar,scylladb/seastar,syuu1228/seastar