Update vulnerabilities/improver.py

Co-authored-by: Philippe Ombredanne <pombredanne@gmail.com>

Author: Hritik14

vulnerabilities/improver.py

@@ -81,7 +81,7 @@ class Improver:
     """
 
     @classproperty
-    def qualified_name(self):
+    def qualified_name(cls):
         """
         Fully qualified name prefixed with the module name of the improver used in logging.
         """