Since the Met first announced the new “Tosca” 10 months ago, the David McVicar production has lost its star tenor, Jonas Kaufmann; the soprano singing the title role, Kristine Opolais; its conductor, Andris Nelsons, who is married to Ms. Opolais; and his replacement, James Levine, who was suspended this month after being accused of sexual misconduct. Now the last remaining star of the originally-announced cast has withdrawn.