fuse.py use correct prefix for extracting clones

due to the error in the prefix usage, we were extracting all clones from
the file instead of the top N, leading to horrendous performance issues.

tools/fuse.py

@@ -718,7 +718,7 @@ def main():
     f = []
 
     vparser = VidjilParser()
-    vparser.addPrefix('clones', 'clones.item.top', le, args.top)
+    vparser.addPrefix('clones.item', 'clones.item.top', le, args.top)
     for path_name in files:
         json_clones = vparser.extract(path_name)
         clones = json.loads(json_clones)