docs: fix incorrect documentation links & formatting (#2332)

The streams documentation referred to module-level 'split' doc which is no longer there

tokio/src/net/tcp/stream.rs

@@ -614,9 +614,6 @@ impl TcpStream {
 
     /// Splits a `TcpStream` into a read half and a write half, which can be used
     /// to read and write the stream concurrently.
-    ///
-    /// See the module level documenation of [`split`](super::split) for more
-    /// details.
     pub fn split(&mut self) -> (ReadHalf<'_>, WriteHalf<'_>) {
         split(self)
     }

tokio/src/net/udp/socket.rs

@@ -74,9 +74,6 @@ impl UdpSocket {
     /// Splits the `UdpSocket` into a receive half and a send half. The two parts
     /// can be used to receive and send datagrams concurrently, even from two
     /// different tasks.
-    ///
-    /// See the module level documenation of [`split`](super::split) for more
-    /// details.
     pub fn split(self) -> (RecvHalf, SendHalf) {
         split(self)
     }

tokio/src/net/unix/stream.rs

@@ -111,9 +111,6 @@ impl UnixStream {
 
     /// Split a `UnixStream` into a read half and a write half, which can be used
     /// to read and write the stream concurrently.
-    ///
-    /// See the module level documenation of [`split`](super::split) for more
-    /// details.
     pub fn split(&mut self) -> (ReadHalf<'_>, WriteHalf<'_>) {
         split(self)
     }

tokio/src/sync/mpsc/error.rs

@@ -96,7 +96,7 @@ impl Error for TryRecvError {}
 
 // ===== ClosedError =====
 
-/// Error returned by [`Sender::poll_ready`](super::Sender::poll_ready)].
+/// Error returned by [`Sender::poll_ready`](super::Sender::poll_ready).
 #[derive(Debug)]
 pub struct ClosedError(());