add unstable cfg to FromStream/IntoStream

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

src/stream/from_stream.rs

@@ -10,6 +10,7 @@ use std::pin::Pin;
 /// See also: [`IntoStream`].
 ///
 /// [`IntoStream`]: trait.IntoStream.html
+#[cfg_attr(feature = "docs", doc(cfg(unstable)))]
 pub trait FromStream<T: Send> {
     /// Creates a value from a stream.
     ///

src/stream/into_stream.rs

@@ -13,6 +13,7 @@ use futures_core::stream::Stream;
 /// See also: [`FromStream`].
 ///
 /// [`FromStream`]: trait.FromStream.html
+#[cfg_attr(feature = "docs", doc(cfg(unstable)))]
 pub trait IntoStream {
     /// The type of the elements being iterated over.
     type Item;