Update turtledemo docstrings with correct file names

[Wulian233]

Bug report

Bug description:

In #123370 , I discussed with Terry some measures to modernize the turtledemo. This requires changes to each file. First, I want to modify the incorrect comment file names, which is the easiest to review. There are five measures to modify, e.g German function names and parameter names, change ISO format time, and others focus on clock.py. I have already completed 2 in my initial commit in a0b922f , but I later reverted the changes due to backporting

From previous discussion:

I'd like to see a follow-up 'modernize PR to

Replace module docstring with "turtledemo/clock.py -- clock program showing time and date." File name is wrong and instruction only applies when run in turtledemo, which it is redundant.

(clock.py fixed)

This issue is a bug fix, not a modernization enhancement?

Linked PRs

• gh-125665: Update turtledemo docstrings with correct file names #125691