Removed the incorrect required value.

composer.json

@@ -1,8 +1,5 @@
 {
   "name": "semantic/ui",
-  "require": {
-      "build": "*"
-  },
   "version"     : "0.3.5",
   "description" : "Semantic empowers designers and developers by creating a shared vocabulary for UI.",
   "homepage"    : "http://www.semantic-ui.com",