Increase language selection form to full width

- The width of the content area is small now so it is okay.

Signed-off-by: Manish Tripathy <manisht@thougtworks.com>
Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Sunil Mohan Adapa <sunil@medhas.org>

plinth/templates/language-selection.html

@@ -22,15 +22,13 @@
 
 {% load bootstrap %}
 
-{% block content_row %}
-  <div class="col-md-6 col-md-offset-3">
-    <form method="post">
-      {% csrf_token %}
+{% block content %}
+  <form method="post">
+    {% csrf_token %}
 
-      {{ form|bootstrap }}
+    {{ form|bootstrap }}
 
-      <input type="submit" class="btn btn-primary"
-             value="{% trans "Save Changes" %}"/>
-    </form>
-  </div>
+    <input type="submit" class="btn btn-primary"
+           value="{% trans "Save Changes" %}"/>
+  </form>
 {% endblock %}