Remove mention of missing_doc_code_examples lint from rustdoc book

Author: GuillaumeGomez

src/doc/rustdoc/src/unstable-features.md

@@ -38,6 +38,15 @@ future.
 Attempting to use these error numbers on stable will result in the code sample being interpreted as
 plain text.
 
+### `missing_doc_code_examples` lint
+
+This lint will emit a warning if an item doesn't have a code example in its documentation.
+It can be enabled using:
+
+```rust,ignore (nightly)
+#![deny(rustdoc::missing_doc_code_examples)]
+```
+
 ## Extensions to the `#[doc]` attribute
 
 These features operate by extending the `#[doc]` attribute, and thus can be caught by the compiler

src/doc/rustdoc/src/write-documentation/what-to-include.md

@@ -39,9 +39,7 @@ warning: 1 warning emitted
 As a library author, adding the lint `#![deny(missing_docs)]` is a great way to
 ensure the project does not drift away from being documented well, and
 `#![warn(missing_docs)]` is a good way to move towards comprehensive
-documentation.  In addition to docs, `#![deny(rustdoc::missing_doc_code_examples)]`
-ensures each function contains a usage example.  In our example above, the
-warning is resolved by adding crate level documentation.
+documentation.
 
 There are more lints in the upcoming chapter [Lints][rustdoc-lints].