removes parkowner legacy field
removes parkowner legacy field

after data migration

MAPC/bostonparks,codeforboston/bostongreenmap,varmas/bostongreenmap,varmas/bostongreenmap,varmas/bostongreenmap,codeforboston/bostongreenmap,varmas/bostongreenmap,MAPC/bostonparks,codeforboston/bostongreenmap,varmas/bostongreenmap,codeforboston/bostongreenmap,codeforboston/bostongreenmap