messaging_service: remove unused include of db/system_keyspace.hh
messaging_service: remove unused include of db/system_keyspace.hh

As a followup to eba20c7e5de6e39dda45bce37670b3fdd5d197a8
"messaging_service: init_local_preferred_ip_cache: get preferred ips from caller".

Signed-off-by: Benny Halevy <23c997c90eb8537635e9392d48e7af1bf1b2ca22@scylladb.com>
Message-Id: <20211123080457.1247970-1-23c997c90eb8537635e9392d48e7af1bf1b2ca22@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla