docs: fix some docs links (#7654)

Author: Darksonn

tokio-util/src/codec/mod.rs

@@ -313,7 +313,7 @@
 //! [`AsyncWrite`]: tokio::io::AsyncWrite
 //! [`Stream`]: futures_core::Stream
 //! [`Sink`]: futures_sink::Sink
-//! [`SinkExt`]: futures::sink::SinkExt
+//! [`SinkExt`]: https://docs.rs/futures/0.3/futures/sink/trait.SinkExt.html
 //! [`SinkExt::close`]: https://docs.rs/futures/0.3/futures/sink/trait.SinkExt.html#method.close
 //! [`FramedRead`]: struct@crate::codec::FramedRead
 //! [`FramedWrite`]: struct@crate::codec::FramedWrite

tokio/src/runtime/mod.rs

@@ -177,7 +177,6 @@
 //! [`tokio::main`]: ../attr.main.html
 //! [runtime builder]: crate::runtime::Builder
 //! [`Runtime::new`]: crate::runtime::Runtime::new
-//! [`Builder::threaded_scheduler`]: crate::runtime::Builder::threaded_scheduler
 //! [`Builder::enable_io`]: crate::runtime::Builder::enable_io
 //! [`Builder::enable_time`]: crate::runtime::Builder::enable_time
 //! [`Builder::enable_all`]: crate::runtime::Builder::enable_all

tokio/src/sync/broadcast.rs

@@ -1170,7 +1170,7 @@ impl<T> Receiver<T> {
     /// Returns true if there aren't any messages in the channel that the [`Receiver`]
     /// has yet to receive.
     ///
-    /// [`Receiver]: create::sync::broadcast::Receiver
+    /// [`Receiver`]: crate::sync::broadcast::Receiver
     ///
     /// # Examples
     ///