Added nox testing for python 3.12.0
Added python 3.12 as a testing option for nox. Needed to limit this to python 3.12.0 since the python requirement for gdptools is <=3.12.
Added python 3.12 as a testing option for nox. Needed to limit this to python 3.12.0 since the python requirement for gdptools is <=3.12.