Update react monorepo to v16.8.6 (#764)

Author: renovate[bot]

src/React.Core/package-lock.json

@@ -12,8 +12,8 @@
     "babel-preset-stage-0": "6.24.1",
     "babel-standalone": "6.26.0",
     "prop-types": "15.7.2",
-    "react": "16.8.5",
-    "react-dom": "16.8.5",
+    "react": "16.8.6",
+    "react-dom": "16.8.6",
     "webpack": "4.29.6",
     "webpack-cli": "3.3.0"
   }