Fix another jinjaism

src/copyvios/templates/support/cv_result.html.jinja

@@ -123,9 +123,9 @@
                 No sources checked.
             </div>
         {% endif %}
-        {% if len(result.sources) > 10 %}
+        {% if result.sources | length > 10 %}
             <div id="cv-additional" class="cv-source-footer">
-                {{ len(result.sources) - 10 }} URL{{ "s" if len(result.sources) > 11 else "" }} with lower similarity hidden. <a id="show-additional-sources" href="#">Show them.</a>
+                {{ result.sources | length - 10 }} URL{{ "s" if result.sources | length > 11 else "" }} with lower similarity hidden. <a id="show-additional-sources" href="#">Show them.</a>
             </div>
         {% endif %}
         {% if skips or result.possible_miss %}