Fix three trivial warnings.

Signed-off-by: Dominic Cooney <dominic.cooney@gmail.com>

components/canvas_traits/webgl_channel/mpsc.rs

@@ -5,7 +5,6 @@
 use serde::{Deserialize, Serialize};
 use serde::{Deserializer, Serializer};
 
-#[macro_use]
 macro_rules! unreachable_serializable {
     ($name:ident) => {
         impl<T> Serialize for $name<T> {

components/media/media_channel/mpsc.rs

@@ -6,7 +6,6 @@ use serde::{Deserialize, Serialize};
 use serde::{Deserializer, Serializer};
 use std::sync::mpsc;
 
-#[macro_use]
 macro_rules! unreachable_serializable {
     ($name:ident) => {
         impl<T> Serialize for $name<T> {

components/script/lib.rs

@@ -2,7 +2,6 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
-#![feature(assoc_char_funcs)]
 #![feature(const_fn_fn_ptr_basics)]
 #![feature(const_fn_trait_bound)]
 #![feature(core_intrinsics)]