move_ref_pattern: adjust error index

src/librustc_error_codes/error_codes/E0009.md

@@ -1,3 +1,5 @@
+#### Note: this error code is no longer emitted by the compiler.
+
 In a pattern, all values that don't implement the `Copy` trait have to be bound
 the same way. The goal here is to avoid binding simultaneously by-move and
 by-ref.
@@ -6,7 +8,9 @@ This limitation may be removed in a future version of Rust.
 
 Erroneous code example:
 
-```compile_fail,E0009
+```
+#![feature(move_ref_pattern)]
+
 struct X { x: (), }
 
 let x = Some((X { x: () }, X { x: () }));