Define helpy dependency via .whl instead of submodule

It also bumps the helpy version.
(I cannot separate these commits since there is
a schemas .whl "schemas (0.0.1.dev283+db2351d)"
missing in the schemas package registry -
someone forgot to push that .whl using CI manual job
but since some newer time schemas
automatically push their .whl to the registry
this is no longer an issue)