Bump @angular/router from 20.3.13 to 21.0.0 in /web_embedding/ng-flutter

Bumps [@angular/router](https://github.com/angular/angular/tree/HEAD/packages/router) from 20.3.13 to 21.0.0.
- [Release notes](https://github.com/angular/angular/releases)
- [Changelog](https://github.com/angular/angular/blob/main/CHANGELOG.md)
- [Commits](https://github.com/angular/angular/commits/21.0.0/packages/router)

---
updated-dependencies:
- dependency-name: "@angular/router"
  dependency-version: 21.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

web_embedding/ng-flutter/package.json

@@ -20,7 +20,7 @@
     "@angular/material": "^20.1.0",
     "@angular/platform-browser": "^20.0.3",
     "@angular/platform-browser-dynamic": "^20.1.0",
-    "@angular/router": "^20.0.3",
+    "@angular/router": "^21.0.0",
     "rxjs": "~7.8.1",
     "tslib": "^2.6.2",
     "zone.js": "~0.15.0"