Bump @angular/material in /web_embedding/ng-flutter

Bumps [@angular/material](https://github.com/angular/components) from 20.2.14 to 21.0.0.
- [Release notes](https://github.com/angular/components/releases)
- [Changelog](https://github.com/angular/components/blob/main/CHANGELOG.md)
- [Commits](https://github.com/angular/components/compare/20.2.14...21.0.0)

---
updated-dependencies:
- dependency-name: "@angular/material"
  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

@@ -17,7 +17,7 @@
     "@angular/compiler": "^20.0.6",
     "@angular/core": "^20.0.3",
     "@angular/forms": "^20.1.2",
-    "@angular/material": "^20.1.0",
+    "@angular/material": "^21.0.0",
     "@angular/platform-browser": "^20.0.3",
     "@angular/platform-browser-dynamic": "^20.1.0",
     "@angular/router": "^20.0.3",