Remove "babel-core" and other babel 6 modules.

Summary: We are using babel 7 and should not be using babel 6 any longer, this removes some references to babel 6 modules.

Reviewed By: yungsters

Differential Revision: D13137326

fbshipit-source-id: 4a2db84522e5613f72a8005f0b1e9943e815f9ec

package.json

@@ -214,10 +214,10 @@
   },
   "devDependencies": {
     "@babel/core": "^7.0.0",
+    "@babel/generator": "^7.0.0",
     "@reactions/component": "^2.0.2",
     "async": "^2.4.0",
     "babel-eslint": "9.0.0",
-    "babel-generator": "^6.26.0",
     "detox": "9.0.4",
     "coveralls": "^3.0.2",
     "eslint": "5.1.0",