Allow disabling typehints in API signatures

Showing type hints can make the rendered version of the docs quite unreadable, and it'd be nice to be able to disable that. In Sphinx you could do that by [setting a parameter](https://www.sphinx-doc.org/en/master/usage/extensions/autodoc.html#confval-autodoc_typehints).

An example of where it'd be nice not to have type hints is this one:


Especially since we repeat the types in our docstrings, they don't need to be present in the method/function signature.

cc @LysandreJik