`gather_results` is no longer exported

[ppm1337]

The function gather_results is still referenced in the docs by functions such as plot_all_cell_types but is not exported anymore (since 19fb2d4). Hence, gather_results is neither available in the spacexr namespace, nor in the Roxygen docs.

For a user, a workaround is to use gather_results via the ::: operator (access of not exported functions). Please clarify if there's a replacement that should be used instead or if this is unintended.