Merge #19890: refactor: remove unused header <arpa/inet.h> in protocol.cpp

2f79e9d refactor: remove unused header <arpa/inet.h> in protocol.cpp (Sebastian Falbesoner)

Pull request description:

  There is no code using types or functions related to "internet operations" anymore in protocol.cpp (since #735, more than 8 years ago!), hence the header include can be removed.

ACKs for top commit:
  practicalswift:
    ACK 2f79e9d -- patch looks correct and CI is happy
  epson121:
    Code review ACK 2f79e9d
  laanwj:
    ACK 2f79e9d
  promag:
    Code review ACK 2f79e9d.

Tree-SHA512: b3f75fa080125a34ce224f11eb13ec7b914cd9930e3bbed24f550031ce92a7e0830e8ff20159d737ffe487dfd28c24c273ad5e89c6932c8c6960d7fadb6c5e54

Author: laanwj

src/protocol.cpp

@@ -8,10 +8,6 @@
 #include <util/strencodings.h>
 #include <util/system.h>
 
-#ifndef WIN32
-# include <arpa/inet.h>
-#endif
-
 static std::atomic<bool> g_initial_block_download_completed(false);
 
 namespace NetMsgType {