Sanitizer example in documentation needs rewriting

[malcolmr]

After #72, the example in the documentation at https://html5lib.readthedocs.io/en/latest/movingparts.html#tokenizers is no longer valid (see also #277).

(Also the links to tokenizer.py and sanitizer.py are both 404.)

[willkg]

This was fixed at some point, but I'm not sure offhand when. The example in the latest docs is correct now. Closing this out.

Thank you for reporting!