Bump rollup from 4.18.1 to 4.21.0

Bumps [rollup](https://github.com/rollup/rollup) from 4.18.1 to 4.21.0.
- [Release notes](https://github.com/rollup/rollup/releases)
- [Changelog](https://github.com/rollup/rollup/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rollup/rollup/compare/v4.18.1...v4.21.0)

---
updated-dependencies:
- dependency-name: rollup
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

src/Umbraco.Web.UI.Client/package.json

@@ -273,7 +273,7 @@
 		"react": "^18.2.0",
 		"react-dom": "^18.2.0",
 		"remark-gfm": "^3.0.1",
-		"rollup": "^4.18.1",
+		"rollup": "^4.21.0",
 		"rollup-plugin-esbuild": "^6.1.1",
 		"rollup-plugin-import-css": "^3.5.0",
 		"rollup-plugin-web-worker-loader": "^1.6.1",