Update react monorepo to v16.8.4

Author: renovate-bot

package-lock.json

@@ -47,8 +47,8 @@
     "jest": "23.6.0",
     "lint-staged": "8.1.5",
     "prettier": "1.16.4",
-    "react": "16.8.3",
-    "react-dom": "16.8.3",
+    "react": "16.8.4",
+    "react-dom": "16.8.4",
     "ts-jest": "23.10.5",
     "tslint": "5.13.1",
     "tslint-config-prettier": "1.18.0",