update release notes for 2.73
update release notes for 2.73

HubSpot/jdbi,pennello/jdbi,jdbi/jdbi,jdbi/jdbi,john9x/jdbi,jdbi/jdbi,hgschmie/jdbi,pennello/jdbi,hgschmie/jdbi,HubSpot/jdbi,hgschmie/jdbi,john9x/jdbi