Remove out-of-date contributors list

To see an up-to-date list, either run `git shortlog -s` in the repo or
visit: https://github.com/graphql/express-graphql/graphs/contributors

Author: wincent

package.json

@@ -2,11 +2,6 @@
   "name": "express-graphql",
   "version": "0.6.6",
   "description": "Production ready GraphQL HTTP middleware.",
-  "contributors": [
-    "Lee Byron <[email protected]> (http://leebyron.com/)",
-    "Daniel Schafer <[email protected]>",
-    "Caleb Meredith <[email protected]>"
-  ],
   "license": "BSD-3-Clause",
   "bugs": {
     "url": "https://github.com/graphql/express-graphql/issues"