DOC: fix Dataframe.to_records examples
- [ ] closes #xxxx
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Fixed the examples of Dataframe.to_records related to timestamp conversion following the changes in default behaviour made in pull request #18902. As requested in issue #18160.