Fix a merge mistake after [syserror].

Author: jyasskin

utilities.html

@@ -552,6 +552,8 @@ <h1>Header &lt;experimental/system_error> synopsis</h1>
 } // namespace fundamentals_v2
 } // namespace experimental
 } // namespace std</code></pre>
+    </cxx-section>
+  </cxx-section>
 
   <cxx-section id="propagate_const">
     <h1>Class template <code>propagate_const</code></h1>