misc: Remove redundant "use" imports

With the nightly toolchain (2024-02-18) cargo check will flag up
redundant imports either because they are pulled in by the prelude on
earlier match.

Remove those redundant imports.

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>

net_util/src/mac.rs

@@ -7,7 +7,6 @@
 
 use std::fmt;
 use std::io;
-use std::result::Result;
 use std::str::FromStr;
 
 use serde::de::{Deserialize, Deserializer, Error};