[3.6] bpo-30781: IDLE: Fix help button on configdialog (GH-3238) (#3489)

This fixes an omission in the ttk conversion patch for this issue, hence no new news.
Patch by Cheryl Sabella.
(cherry picked from commit 3866d9bbcf808cea98b3d00007f9f246b83858ce)
1 file changed