Update PAstro classification for new ligo-em-bright release
The purpose of this MR is to reduce the (duplicated) code in pesummary.gw.classification.PAstro
and instead call the ligo.em_bright.em_bright.source_classification_pe_from_samples
function (see emfollow/em-properties/em-bright!59 (merged)). This cannot be merged until ligo-em-bright
makes a new release.