Update Pesummary cosmology
What?
This MR updates the standard analysis settings to use the astropy rather than the lal implentation of the Planck cosmology.
Who?
This MR was prepared by @daniel-williams.
Why?
In order to maintain consistency between all pipelines and downstream analyses there is an LVK-wide recommendation that the astropy implementation be used going forwards.
Where?
This change affects the cosmology setting passed to PESummary and removes the recalculation of mass posteriors.