gnrc: Clean up unused imports

src/gnrc_util.rs

@@ -11,7 +11,6 @@ use crate::thread::KernelPID;
 
 #[cfg(riot_module_gnrc_udp)]
 use riot_sys::gnrc_nettype_t_GNRC_NETTYPE_UDP as GNRC_NETTYPE_UDP;
-use riot_sys::{gnrc_netif_hdr_t, gnrc_nettype_t_GNRC_NETTYPE_NETIF as GNRC_NETTYPE_NETIF};
 
 /// Trait of data structures that store all the information needed to respond to a Pktsnip in some
 /// way; the data (typically address and port information) is copied into the trait implementation