LONDON (Reuters) – British gymnast Ellie Downie announced her retirement aged 23 “with a heavy heart” on Monday, saying it was time to prioritise her mental health and happiness after a tough few years. Downie was the first Briton to win a major all-around title when she took European gold in 2017 and ends her career with 12 medals at world and European level. She competed at the 2016 Rio de Janeiro Olympics, along with older sister and 2019 world uneven bars silver medallist Becky, but in 2021 decided to take time out of the sport following the death of her brother Josh. “To say it’s been a d…