SAN FRANCISCO — A judge has ordered Elon Musk to testify for a third time as part of the Securities and Exchange Commission’s investigation into his $44 billion purchase of Twitter, now called X, in 2022.Magistrate Judge Laurel Beeler issued an order Saturday giving Musk, his team and the SEC a week to agree on a date and location for Musk’s testimony. In a court hearing last December, Beeler said she would issue an order if the two sides couldn’t agree on when and where the Tesla and SpaceX CEO …