[mod] simple theme: drop img_src from default results

The use of img_src AND thumbnail in the default results makes no sense (only a
thumbnail is needed).  In the current state this is rather confusing, because
img_src is displayed like a thumbnail (small) and thumbnail is displayed like an
image (large).

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/engines/mixcloud.py

@@ -44,7 +44,7 @@ def response(resp):
             'url': r_url,
             'title': result['name'],
             'iframe_src': iframe_src.format(url=r_url),
-            'img_src': result['pictures']['medium'],
+            'thumbnail': result['pictures']['medium'],
             'publishedDate': publishedDate,
             'content': result['user']['name'],
         }