Update react monorepo to v16

Author: renovate-bot

package.json

@@ -9,7 +9,7 @@
     "babel-runtime": "6.26.0",
     "core-js": "2.5.7",
     "meteor-node-stubs": "0.4.1",
-    "react": "15.6.2",
-    "react-dom": "15.6.2"
+    "react": "16.8.1",
+    "react-dom": "16.8.1"
   }
 }