[Nest] Fixed receptor type mismatch in native cell types

In `src/nest/cells.py`, `get_receptor_types` was changed to return a list
instead of a tuple, but `native_cell_type` still compared the returned receptor
types to the old tuple which lead to `standard_receptor_type`-attribute to be
wrongly set to `False`.

This caused problems when creating Projections, for instance, to parrot neurons.