By Matt Audilet All-time great U.S. Olympian Allyson Felix is officially retiring after one final season to close out her incredible track and field career. Felix announced her future retirement with a touching message on Instagram. As a little girl they called chicken legs, never in my wildest dreams would I have imagined I’d have a career like this. I have so much gratitude for this sport that has changed my life. I have given everything I have to running and for the first time I’m not sure if I have anything left to give. I want to say goodbye and thank you to the sport and people who have …