tests: bump example and xml2 version

[moui0]

crateios and cran released new version:

• example
• xml2

[lilydjwg]

The tests no longer work with newer pytest-asyncio, and I haven't figured out why yet. (And it fails differently than on my local machine.)

[yan12125]

With some trials and errors, I managed to get tests working for Python >= 3.8 [1]. How about dropping support for Python 3.7 and call it a day?

[1] https://github.com/yan12125/nvchecker/commits/test-ci/

[lilydjwg]

@yan12125 it works, thank you!