Context

#830 introduces proper typing annotations for allure.step via @typing.overload.

This PR removes the annotations from the implementation as per the Python docs:

The @overload-decorated definitions are for the benefit of the type checker only, since they will be overwritten by the non-@overload-decorated definition, while the latter is used at runtime but should be ignored by a type checker.

It also disables type checking of the wrapper function returned by StepContext.__call__ (it can't be typechecked without ParamSpec, which is only available in Python 3.10+).