Drop some dead imports of imp

Lib/idlelib/PathBrowser.py

 import os
 import sys
-import imp
 import importlib.machinery
 
 from idlelib.TreeWidget import TreeItem

Lib/idlelib/TreeWidget.py

@@ -16,7 +16,6 @@
 
 import os
 from tkinter import *
-import imp
 
 from idlelib import ZoomHeight
 from idlelib.configHandler import idleConf

Misc/NEWS

@@ -81,6 +81,8 @@ Library
 IDLE
 ----
 
+- Remove dead imports of imp.
+
 - Issue #18196: Avoid displaying spurious SystemExit tracebacks.
 
 - Issue #5492: Avoid traceback when exiting IDLE caused by a race condition.