Fix typo

Author: lnicola

generated_features.adoc

@@ -641,7 +641,7 @@ intraDocLink:: Emitted for intra doc links in doc-strings.
 library:: Emitted for items that are defined outside of the current crate.
 mutable:: Emitted for mutable locals and statics as well as functions taking `&mut self`.
 public:: Emitted for items that are from the current crate and are `pub`.
-reference: Emitted for locals behind a reference and functions taking `self` by reference.
+reference:: Emitted for locals behind a reference and functions taking `self` by reference.
 static:: Emitted for "static" functions, also known as functions that do not take a `self` param, as well as statics and consts.
 trait:: Emitted for associated trait items.
 unsafe:: Emitted for unsafe operations, like unsafe function calls, as well as the `unsafe` token.