Fix lint name formatting

Author: blyxyas

book/src/development/emitting_lints.md

@@ -34,7 +34,7 @@ method based on what we need for the lint at hand.
 
 ### Implement Trait Method
 
-Assume that we have added and defined a `BarExpressions` lint, we could write
+Assume that we have added and defined a `bar_expressions` lint, we could write
 down a skeleton for this lint as the following:
 
 ```rust