MIAMI — After a two-year pandemic hiatus, the Ultra Music Festival returns to Miami this weekend – back downtown after a brief and problematic interlude on Virginia Key. For festival veterans, it’ll feel like 2018 again. That’s because Ultra organizers aren’t requiring proof of vaccination, a negative COVID-19 test or masks for entry. Though the festival will make available free masks to any ticket holder who wants one, the addition of hand sanitizing and hand-washing stations will likely be the only visible remnant of a pandemic that derailed the three-day electronic music extravaganza for th…