bpo-43013: Update idlelib code to 3.x  (GH-24315)

Remove 9 remaining '(object)' occurrences in class headers in idlelib
and 25 '()' occurrences in idlelib.idle_test class headers.
diff --git a/Lib/idlelib/tooltip.py b/Lib/idlelib/tooltip.py
index 6965826..d714318 100644
--- a/Lib/idlelib/tooltip.py
+++ b/Lib/idlelib/tooltip.py
@@ -7,7 +7,7 @@
 from tkinter import *
 
 
-class TooltipBase(object):
+class TooltipBase:
     """abstract base class for tooltips"""
 
     def __init__(self, anchor_widget):