What does Jacosta call Polybus’s death?

Unbeknownst to Oedipus, Polybus isn't his real father. The king of Corinth adopted Oedipus as his own son after he was left to die by his real parents—Laius and Jocasta—on Mount Cithaeron shortly after he was born. The oracle had prophesied that Oedipus would one day kill his father, so a horrified Laius decided to expose the baby Oedipus to the elements to ensure that this terrible prophecy would never be fulfilled. Years later, however, the prophecy comes back to haunt Laius, as indeed it haunts Oedipus and Jocasta.
But before it does, news arrives in Thebes that Polybus has died. Jocasta is overjoyed. She reasons that as Polybus has died from natural causes then the prophecy must not have been true after all; Oedipus has not killed his father. Oedipus rejoices with his wife—who unbeknownst to him is actually his real mother—as a huge weight appears to have been lifted from his shoulders. Or as Jocasta puts it, Polybus's death "lights out darkness much."