change path to tests.yml - cleanup after separating pypi and tests

[AgnieszkaZaba]

Adressess #1470
I hope it fix it.

[slayoo]

It is not related to #1470, but of course worth fixing!
The checksum fixed here is used to trigger cache regeneration for pip package cache in the examples job in CI.

In #1470, the problem is that setuptools_scm stopped taking into account our custom version string setup:

PySDM/setup.py

Line 28 in 4171cfc

use_scm_version={"local_scheme": lambda _: "", "version_scheme": "post-release"},

Without it, the version string contains commit hash, what makes the package wheel names incompatible with PyPI requirements.

[AgnieszkaZaba]

Thanks @slayoo!