chore: bump to newer nightly (#1485)

tokio-executor/src/threadpool/blocking.rs

@@ -80,8 +80,6 @@ pub struct BlockingError {
 /// that needs to be performed.
 ///
 /// ```rust
-/// #![feature(async_await)]
-///
 /// use tokio_executor::threadpool::{ThreadPool, blocking};
 ///
 /// use futures_util::future::poll_fn;

tokio-executor/src/threadpool/builder.rs

@@ -32,8 +32,6 @@ use std::time::Duration;
 /// # Examples
 ///
 /// ```
-/// #![feature(async_await)]
-///
 /// use tokio_executor::threadpool::Builder;
 ///
 /// use std::time::Duration;

tokio-executor/src/threadpool/sender.rs

@@ -59,8 +59,6 @@ impl Sender {
     /// # Examples
     ///
     /// ```rust
-    /// #![feature(async_await)]
-    ///
     /// use tokio_executor::threadpool::ThreadPool;
     ///
     /// // Create a thread pool with default configuration values

tokio-executor/src/threadpool/thread_pool.rs

@@ -51,8 +51,6 @@ impl ThreadPool {
     /// # Examples
     ///
     /// ```rust
-    /// #![feature(async_await)]
-    ///
     /// use tokio_executor::threadpool::ThreadPool;
     ///
     /// // Create a thread pool with default configuration values