Temporarily downgrade demo to 2.2.3 due to StackBlitz npm cache issue

The current version gives a `Failure: unsatisfied version range` error on StackBlitz. Normally it only takes a couple of minutes for the published version to become visible, but it looks like sometimes the cache needs a manual push. (stackblitz/core#624)

Author: Oblosys

examples/parent-child-demo/package.json

@@ -15,6 +15,6 @@
     "react": "16.8.6",
     "react-dom": "16.8.6",
     "react-hot-loader": "4.11.1",
-    "react-lifecycle-visualizer": "^2.2.4"
+    "react-lifecycle-visualizer": "^2.2.3"
   }
 }