Update gdal import

Gdal is being imported in the `__inti__.py` inside of the io module using find_spec and manually loading the module.

This can lead to problems within a jupyter notebook where plio can't find gdal due to the way packages are handled in conda envs.

This could probably be changed to a try except around the usual import method.

https://github.com/USGS-Astrogeology/plio/blob/baf43c4296b51cb1cbb7dfacd783f456605677d6/plio/io/__init__.py#L6