Update react-on-rails to 16.0.1-rc.4 in package.json files

Keep JavaScript dependencies in sync with Ruby Gemfile versions

Author: ihabadham

spec/execjs-compatible-dummy/package.json

@@ -29,7 +29,7 @@
     "prop-types": "^15.8.1",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
-    "react-on-rails": "15.0.0",
+    "react-on-rails": "16.0.1-rc.4",
     "shakapacker": "8.0.0",
     "style-loader": "^4.0.0",
     "terser-webpack-plugin": "5",