Move `types-` stub packages to dev dependencies

[y4n9squared]

We wanted to upgrade our library from 0.1.5 to 0.2 but noticed that stub packages have been added and are propagated to the users.

As a library maintainer, you have no way of knowing which versions of the stubs are required by applications as they perform their own lock with a superset of constraints.

In addition, it is also very hard to keep the stub packages consistent with the libraries they are supposed to annotate (e.g. your own lock file resolved PyYAML 6.0.2 but your stubs are for PyYAML 6.0.12 which means your static analysis is not reflective of whether the types are actually consistent or not.

Would it be possible to move types-pyyaml and types-python-dateutil to dev dependencies?

Thank you!