By Victoria Johns Victoria Beckham reckons she’s not afraid of the big 5-0 as she shared a love letter to her family on her birthday today. The artist formerly known as Posh Spice is celebrating the milestone in a four-day event with her husband David, kids Brooklyn, Romeo, Cruz and Harper along with her parents and close friends. Telling her 33 million followers, she’s “only just getting started”, she thanked her family for believing in her and giving her the courage to “dream big and then dream bigger”. In a post on Instagram in which she shared a snap of herself sporting one of her own desi…