IPV6_ROUTER_ALERT_ISOLATE looks too recent for test env

Signed-off-by: Arthur Gautier <baloo@gandi.net>

Author: Arthur Gautier

src/unix/linux_like/mod.rs

@@ -835,7 +835,6 @@ pub const IPV6_V6ONLY: ::c_int = 26;
 pub const IPV6_JOIN_ANYCAST: ::c_int = 27;
 pub const IPV6_LEAVE_ANYCAST: ::c_int = 28;
 pub const IPV6_MULTICAST_ALL: ::c_int = 29;
-pub const IPV6_ROUTER_ALERT_ISOLATE: ::c_int = 30;
 pub const IPV6_RECVPKTINFO: ::c_int = 49;
 pub const IPV6_PKTINFO: ::c_int = 50;
 pub const IPV6_RECVTCLASS: ::c_int = 66;