Bump serialize-javascript from 2.1.2 to 4.0.0 in /examples/rails

Bumps [serialize-javascript](https://github.com/yahoo/serialize-javascript) from 2.1.2 to 4.0.0.
- [Release notes](https://github.com/yahoo/serialize-javascript/releases)
- [Commits](yahoo/serialize-javascript@v2.1.2...v4.0.0)

Signed-off-by: dependabot[bot] <support@github.com>

examples/rails/package.json

@@ -10,7 +10,7 @@
     "babel-loader": "^8.0.6",
     "chart.js": "^2.8.0",
     "chartkick": "^3.1.1",
-    "serialize-javascript": "^2.1.1",
+    "serialize-javascript": "^4.0.0",
     "turbolinks": "^5.2.0",
     "webpack": "^4.41.1",
     "webpack-cli": "^3.3.9"