Fix signature to_string

jedi/evaluate/signature.py

@@ -25,8 +25,10 @@ class AbstractSignature(object):
                     yield '/'
                     is_positional = False
 
-                if kind == Parameter.KEYWORD_ONLY and not is_kw_only:
-                    yield '*,'
+                if kind == Parameter.VAR_POSITIONAL:
+                    is_kw_only = True
+                elif kind == Parameter.KEYWORD_ONLY and not is_kw_only:
+                    yield '*'
                     is_kw_only = True
 
                 yield n.to_string()