Fix expectations after #653 (#657)

Author: arv

test/fixture/html/nested.config-output.html

@@ -218,7 +218,7 @@ <h3 class='mb0 no-anchor'></h3>
 
             <div class='keyline-top-not py2'><section class='py2 clearfix'>
 
-  <h2 id='Highlighted section' class='mt0'>
+  <h2 id='highlighted-section' class='mt0'>
     Highlighted section
   </h2>