fix(CONTRIBUTING.md): correct markdown link (#1932)
fix(CONTRIBUTING.md): correct markdown link (#1932)

Small correction of a link to the editor section of Prettier
[link] -> (link)
cjohansen/Sinon.JS,cjohansen/Sinon.JS,mroderick/Sinon.JS,fatso83/Sinon.JS,fatso83/Sinon.JS,cjohansen/Sinon.JS,mroderick/Sinon.JS,mroderick/Sinon.JS,fatso83/Sinon.JS