compute/xmpp_wikibot missing tests and not compatible with 3.10

[leahecole]

Hi! I noticed that this sample is failing Python 3.10 periodic tests and wanted to highlight a a few things and propose possible solutions

Problems

• This sample is missing tests - if it's going to stick around, we should have some system tests for it!
• This sample relies on a library that is very deprecated which is why it does not work for 3.10
• This doesn't appear anywhere in the docs

Possible solutions

• Remove this sample - if folks aren't using this sample, the easiest way to update it is to remove it! 😁
• Update this sample to add a test and a [noxfile_config.py](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/noxfile_config.py) that excludes Python 3.10
• Update this sample to add a test and refactor it to use slixmpp

Please reach out to me or anyone in @GoogleCloudPlatform/python-samples-owners for recommendations and since I know office hours aren't in a great time zone for you also feel free to set up time that is during your work hours to chat if you'd like!

[m-strzelczyk]

I think we should just delete this sample. There's not point in showing an example with deprecated library. Especially, since it's not even mentioned in our public docs.

I'll prepare a PR removing it.