Improve documention for tkinter.messagebox

[serhiy-storchaka]

Linked PRs

• gh-111576: Improve documention for tkinter.messagebox #111578
• [3.12] gh-111576: Improve documention for tkinter.messagebox (GH-111578) #111597
• [3.11] gh-111576: Improve documention for tkinter.messagebox (GH-111578) #111598