Bump @angular/cli from 20.1.6 to 21.0.0 in /web_embedding/ng-flutter

Bumps [@angular/cli](https://github.com/angular/angular-cli) from 20.1.6 to 21.0.0.
- [Release notes](https://github.com/angular/angular-cli/releases)
- [Changelog](https://github.com/angular/angular-cli/blob/main/CHANGELOG.md)
- [Commits](https://github.com/angular/angular-cli/compare/20.1.6...21.0.0)

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

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

web_embedding/ng-flutter/package.json

@@ -27,7 +27,7 @@
   },
   "devDependencies": {
     "@angular-devkit/build-angular": "^20.0.2",
-    "@angular/cli": "~20.1.0",
+    "@angular/cli": "~21.0.0",
     "@angular/compiler-cli": "^20.0.3",
     "@types/jasmine": "~5.1.0",
     "jasmine-core": "~5.5.0",