fix(package.json): remove es6-promise from the peerDependency list

As of zone.js@0.6* we no longer require an es6-promise polyfill. The polyfill is only needed on browsers that don't
have native Promise support.

modules/benchpress/package.json

@@ -10,7 +10,6 @@
   "repository": <%= JSON.stringify(packageJson.repository) %>,
   "dependencies": {
     "angular2": "<%= packageJson.version %>",
-    "es6-promise": "<%= packageJson.dependencies['es6-promise'] %>",
     "es6-shim": "<%= packageJson.dependencies['es6-shim'] %>",
     "reflect-metadata": "<%= packageJson.dependencies['reflect-metadata'] %>",
     "rxjs": "<%= packageJson.dependencies['rxjs'] %>",