Update pesummary.gw.cosmology module to handle astropy==5.1
The purpose of this MR is to update how pesummary grabs a list of available cosmologies from astropy in order to be compatible with astropy==5.1.
Maintenance will be performed on git.ligo.org, containers.ligo.org, and docs.ligo.org on Tuesday 24 September 2024 starting at approximately 9am PDT. It is expected to take around 30 minutes and there will be several periods of downtime throughout the maintenance. Please address any comments, concerns, or questions to the helpdesk.
The purpose of this MR is to update how pesummary grabs a list of available cosmologies from astropy in order to be compatible with astropy==5.1.