Remove useless tests configuration

src/test/valid_token_with_custom_increment.rs

@@ -13,7 +13,7 @@ fn port(index: u16) -> u16 {
     get_port_number(PortsAllocation::ValidTokenWithCustomIncrement, index)
 }
 
-#[tokio::test(flavor = "multi_thread")]
+#[tokio::test()]
 async fn test() {
     let _ = env_logger::builder().is_test(true).try_init();