By Nicola Methven Doctor Who companion Millie Gibson is being dropped from the BBC sci-fi show and will be replaced for Ncuti Gatwa’s second series by actress Varada Seethu. The decision by showrunner Russell T Davies to write out the former Coronation Street star, who plays orphan Ruby Sunday, was made last year after filming on her first run ended. The shock twist will come as a surprise to fans who only watched her on-screen debut in the festive episode last month. Now Millie, 19, will not appear in the 2024 Christmas special later this year and will make only a handful of appearances acros…