about.html: balance open/close for tags (#677)

Author: pjonsson

wwwroot/about.html

@@ -63,7 +63,7 @@
     <div class="row">
     <div class="col-sm-9">
 
-    <h1>About the NationalMap</h2>
+    <h1>About the NationalMap</h1>
 
       <p>The <strong>NationalMap</strong> is a website for map-based access to spatial data from Australian government agencies.
       It is an initiative of the Department of Communications and the Arts now currently managed by the Department of the Prime Minister and Cabinet and the software has been developed by Data61 working closely with the Department of Communications and the Arts, Geoscience Australia and other government agencies.</p>