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>

vhost_user_block/src/lib.rs

@@ -29,7 +29,6 @@ use std::result;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex, RwLock, RwLockWriteGuard};
 use std::time::Instant;
-use std::vec::Vec;
 use std::{convert, error, fmt, io};
 use vhost::vhost_user::message::*;
 use vhost::vhost_user::Listener;