Add 3.14 to Trove classifiers

[Tinche]

See title.

[webknjaz]

Is there a policy for this in the project? I'm my own, I usually add a new classifier to signal that it's tested against a stable version of that project, not during the alpha phase of CPython..

[hynek]

The policy is that the CI runs against our trove classifiers which implies that it works.