Fix 404 error on banniere-en.png

Filename was incorrect and was using an underscore instead of a dash.

src/memopol/templates/home.html

@@ -18,7 +18,7 @@
       <p>
         {{ HOMEPAGE_INTRO_TEXT }}
       </p>
-      <img src="{% static "images/banniere_en.png" %}" alt=""/>
+      <img src="{% static "images/banniere-en.png" %}" alt=""/>
       <h2>{% trans "What about this instance ?" %}</h2>
       <p>
         {{ HOMEPAGE_INSTANCE_TEXT }}