bpo-30781: IDLE: Fix help button on configdialog (#3238)

This fixes an omission in the ttk conversion patch for this issue, hence no new news.
Patch by Cheryl Sabella.

Author: csabella

Lib/idlelib/configdialog.py

@@ -187,12 +187,12 @@ def help(self):
         """Create textview for config dialog help.
 
         Attrbutes accessed:
-            tab_pages
+            note
 
         Methods:
             view_text: Method from textview module.
         """
-        page = self.tab_pages._current_page
+        page = self.note.tab(self.note.select(), option='text').strip()
         view_text(self, title='Help for IDLE preferences',
                  text=help_common+help_pages.get(page, ''))
 
@@ -2104,7 +2104,7 @@ def detach(self):
 [Cancel] only cancels changes made since the last save.
 '''
 help_pages = {
-    'Highlighting': '''
+    'Highlights': '''
 Highlighting:
 The IDLE Dark color theme is new in October 2015.  It can only
 be used with older IDLE releases if it is saved as a custom