Add <code></code> tags to header in JS Boolean doc (consistency) (#2956)

This achieves consistency with a similar header that uses <code></code>
tags, in the same article.

files/en-us/web/javascript/reference/global_objects/boolean/index.html

@@ -72,7 +72,7 @@ <h2 id="Instance_methods">Instance methods</h2>
 
 <h2 id="Examples">Examples</h2>
 
-<h3 id="Creating_Boolean_objects_with_an_initial_value_of_false">Creating Boolean objects with an initial value of false</h3>
+<h3 id="Creating_Boolean_objects_with_an_initial_value_of_false">Creating <code>Boolean</code> objects with an initial value of <code>false</code></h3>
 
 <pre class="brush: js">var bNoParam = new Boolean();
 var bZero = new Boolean(0);