gh-97669: Move difflib examples to Doc/includes/ (#97964)

Remove diff.py and ndiff.py scripts of Tools/scripts/: move them to
Doc/includes/.

* diff.py and ndiff.py files are no longer executable. Remove also
  their shebang ("#!/usr/bin/env python3").
* Remove the -profile command from ndiff.py to simply the code.
* Remove ndiff.py copyright and history command. The Python
  documentation examples are distributed under the "Zero Clause BSD
  License".