React: Bump Canary Version

Reviewed By: gaearon

Differential Revision: D10302487

fbshipit-source-id: 28a00f7076a53dc243ac55ff6c14dc2927318de2

Author: yungsters

package.json

@@ -145,7 +145,7 @@
     "react-native": "local-cli/wrong-react-native.js"
   },
   "peerDependencies": {
-    "react": "16.6.0-alpha.400d197"
+    "react": "16.6.0-alpha.8af6728"
   },
   "dependencies": {
     "@babel/runtime": "^7.0.0",
@@ -220,9 +220,9 @@
     "jest": "23.4.1",
     "jest-junit": "5.1.0",
     "prettier": "1.13.6",
-    "react": "16.6.0-alpha.400d197",
+    "react": "16.6.0-alpha.8af6728",
     "react-native-dummy": "0.1.0",
-    "react-test-renderer": "16.6.0-alpha.400d197",
+    "react-test-renderer": "16.6.0-alpha.8af6728",
     "shelljs": "^0.7.8"
   },
   "detox": {