SOPHIE DAVIES  STELLA Jean, the Haitian-Italian designer who has just announced a boycott of Milan Fashion Week, says she has suffered racism all her life. But it was only when the 41-year-old encountered it in Italy's mainly white fashion industry that she realised just how unwilling people were to talk about it. Now Jean, whose brightly-coloured skirts and dresses are worn by celebrities including Beyonce and Rihanna, says she can no longer remain silent in the face of what she sees as a rise in racially-charged incidents in Italian fashion. The former model, a protege of Giorgio Armani and the…