Rollup merge of rust-lang#56242 - GuillaumeGomez:iterator-missing-link, r=Centril

Add missing link in docs

r? @steveklabnik

Author: Centril

src/libcore/iter/iterator.rs

@@ -162,7 +162,7 @@ pub trait Iterator {
     /// That said, the implementation should provide a correct estimation,
     /// because otherwise it would be a violation of the trait's protocol.
     ///
-    /// The default implementation returns `(0, None)` which is correct for any
+    /// The default implementation returns `(0, `[`None`]`)` which is correct for any
     /// iterator.
     ///
     /// [`usize`]: ../../std/primitive.usize.html