Apply a bunch of clippy lints

src/io.rs

@@ -1,14 +1,8 @@
-use std::{
-    io::{Read, Seek, Write},
-    thread::current,
-};
+use std::io::{Read, Seek, Write};
 
 use anyhow::bail;
 use csv::Position;
-use rmp_serde::{
-    decode::{ReadReader, ReadRefReader, ReadSlice},
-    from_read, Deserializer, Serializer,
-};
+use rmp_serde::{decode::ReadReader, Deserializer, Serializer};
 use serde::{de::DeserializeOwned, Deserialize, Serialize};
 
 pub trait RecordSerializer {