Markup Conventions: Replaced stale mention of Klavika with Cairo

Ref jquery/jquery-wp-content#446

Author: Krinkle

pages/markup-conventions.html

@@ -39,9 +39,9 @@ <h2 id="typography" class="block">Typography</h2>
 <p>The jQuery sites use 4 typefaces. Please see the <a href="http://brand.jquery.org/typography/">Typography</a> section of the jQuery Brand Guidelines for more information about our font choices.</p>
 
 <div class="example">
-	<h3>Klavika</h3>
+	<h3>Cairo</h3>
 
-	<h2>Use Klavika for headings.</h2>
+	<h2>Use Cairo for headings.</h2>
 
 	<p>Also for navigation, buttons &amp; actions.</p>