Rollup merge of rust-lang#119641 - eopb:std-unused-ip-feature, r=ChrisDenton

Remove feature not required by `Ipv6Addr::to_cononical` doctest

The feature does not seem to be required by this doctest.

Author: Nadrieril

library/core/src/net/ip_addr.rs

@@ -1893,7 +1893,6 @@ impl Ipv6Addr {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ip)]
     /// use std::net::Ipv6Addr;
     ///
     /// assert_eq!(Ipv6Addr::new(0, 0, 0, 0, 0, 0xffff, 0x7f00, 0x1).is_loopback(), false);