By Lisa Richwine (Reuters) -Lawyers for “Aquaman” actor Amber Heard decided not to call Johnny Depp back to the witness stand as they wrapped up their defense this week in the former couple’s defamation case, a source close to Heard said on Monday afternoon. Depp appeared on a list of potential witnesses as the trial entered its sixth and final week. “The Pirates of the Caribbean” star could testify again if his own lawyers summon him for more questioning ahead of closing arguments on Friday. Depp, 58, is suing Heard in Virginia for $50 million, saying she defamed him when she said she was a v…