index: fix message that should have been in english

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@enix.org>

www/templates/maposmatic/index.html

@@ -34,7 +34,7 @@
 
 <div id="chavagne">
   <a href="/smedia/chavagne.pdf"><img src="/smedia/chavagne-small.png"/></a><br/>
-  {% trans "Plan de la ville" %}<br/>
+  {% trans "City map" %}<br/>
   <a href="/smedia/chavagne.pdf">PDF</a>
 </div>