Allow InstancePropertyHelper to accept properties with names on Python 3.13+

[hroncok]

Fixes #3761

[mmerickel]

We don't currently have 3.13 in the test suite so I can't trust the cicd here. Perhaps you could add the config for that to this PR and focus it on getting Pyramid working in 3.13?

As a side note, isn't cgi removed in 3.13 such that webob doesn't work on 3.13 so you're hosed anyway until we fix that?

[hroncok]

Perhaps you could add the config for that to this PR and focus it on getting Pyramid working in 3.13?

I can try, but no promises.

As a side note, isn't cgi removed in 3.13 such that webob doesn't work on 3.13 so you're hosed anyway until we fix that?

I use legacy-cgi for that.

[hroncok]

The updated tox config works locally. Hopefully, it also works on the CI (needs your approval).