Bump serialize-javascript from 2.1.2 to 4.0.0 in /sapl-frontend

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](https://github.com/yahoo/serialize-javascript/compare/v2.1.2...v4.0.0)

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

sapl-frontend/package.json

@@ -24,7 +24,7 @@
     "moment": "^2.24.0",
     "moment-locales-webpack-plugin": "^1.1.2",
     "popper.js": "^1.16.1",
-    "serialize-javascript": "^2.1.2",
+    "serialize-javascript": "^4.0.0",
     "terser": "^4.6.11",
     "tinymce": "^4.9.9",
     "tinymce-light-skin": "^1.3.1",