Switch from Array.percentile to weighted_credible_interval
As found in https://git.ligo.org/computing/sccb/-/issues/1408#note_912706, the latest PESummary version breaks CWInPy due to the removal of the Array.percentile
static method in lscsoft/pesummary@90d4bddb. There is instead now the weighted_credible_interval
function that can be used. For this I would need to pin PESummary to be >= 1.1.0. This would also mean dropping Python 3.8 support and only being Python >=3.9 compatible.