devel/py-apscheduler: unbreak with pytest >= 6 after f1d506505d6c

$ make test
[...]

> py38-apscheduler-3.9.1 depends on package: py38-pytest>=3.3<6 - not found

• Error code 1

https://github.com/agronholm/apscheduler/commit/4ded0dceb05a