compat/mingw: drop outdated comment

The part about keeping the original error number hasn't been accurate since
commit c11f75c (mingw: make sure errno is set correctly when socket
operations fail, 2019-11-25) and the part about strerror() not knowing
about these errors is untrue since the previous commit.

Signed-off-by: Matthias Aßhauer <mha1993@live.de>

compat/mingw.c

@@ -2744,15 +2744,6 @@ int mingw_socket(int domain, int type, int protocol)
 	ensure_socket_initialization();
 	s = WSASocket(domain, type, protocol, NULL, 0, 0);
 	if (s == INVALID_SOCKET) {
-		/*
-		 * WSAGetLastError() values are regular BSD error codes
-		 * biased by WSABASEERR.
-		 * However, strerror() does not know about networking
-		 * specific errors, which are values beginning at 38 or so.
-		 * Therefore, we choose to leave the biased error code
-		 * in errno so that _if_ someone looks up the code somewhere,
-		 * then it is at least the number that are usually listed.
-		 */
 		set_wsa_errno();
 		return -1;
 	}