Update kinds_of_types.rst: keep old anchor for #no-strict-optional

[wyattscarpenter]

Addresses #19252 (comment)

support this old anchor, for people on older mypy versions

This way, when people get the old documentation link, it will continue to go to the right place.

I have looked at the documentation that gets generated locally to see if everything still works. It does. In our vast panoply of documentation, we now have two very similar refs, no-strict-optional and no_strict_optional (used in https://mypy.readthedocs.io/en/stable/common_issues.html#no-errors-reported-for-obviously-wrong-code to link to https://mypy.readthedocs.io/en/stable/command_line.html#no-strict-optional) but the software handles them fine, without getting confused.

[wyattscarpenter]

Possibly we should just use clever redirects instead, which is sort of a Sphinx feature to some extent. (Edit: I may one day figure out Sphinx redirects, but for now this fix is fine.)