refactor: remove unused header <arpa/inet.h> in protocol.cpp
refactor: remove unused header <arpa/inet.h> in protocol.cpp

Former-commit-id: ac8997298215c41bb181f6f2b761dfcc805ea929
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin