fix inconsistent spacing in example

Author: meadowsys

src/patterns.md

@@ -231,7 +231,7 @@ To make it valid, write the following:
 #    age: u8,
 # }
 # let value = Person { name: String::from("John"), age: 23 };
-if let Person {name: ref person_name, age: 18..=150 } = value { }
+if let Person { name: ref person_name, age: 18..=150 } = value { }
 ```
 
 Thus, `ref` is not something that is being matched against.