Python: Handle __class_getitem__ in py/not-named-self (#2825)

Fixes #2824

python/ql/src/Functions/NonSelf.ql

@@ -32,6 +32,7 @@ where
         not name = "__new__" and
         not name = "__metaclass__" and
         not name = "__init_subclass__" and
+        not name = "__class_getitem__" and
         /* declared in scope */
         f.getScope() = cls.getScope()
     ) and