fix: failing nightly CI tests (#554)

src/decoder/mod.rs

@@ -4,7 +4,6 @@ use std::error::Error;
 use std::fmt;
 #[allow(unused_imports)]
 use std::io::{Read, Seek, SeekFrom};
-use std::marker::Sync;
 use std::mem;
 use std::str::FromStr;
 use std::time::Duration;

src/decoder/read_seek_source.rs

@@ -1,5 +1,4 @@
 use std::io::{Read, Result, Seek, SeekFrom};
-use std::marker::Sync;
 
 use symphonia::core::io::MediaSource;
 

src/stream.rs

@@ -1,5 +1,4 @@
 use std::io::{Read, Seek};
-use std::marker::Sync;
 use std::sync::{Arc, Weak};
 use std::{error, fmt};