Updated pyproject and README to use astra-toolbox from PyPI
As of July 2024 it seems to have a recent-enough astra-toolbox that we can depent on, see https://pypi.org/project/astra-toolbox/
As of July 2024 it seems to have a recent-enough astra-toolbox that we can depent on, see https://pypi.org/project/astra-toolbox/