Bump @angular/core from 20.3.16 to 21.1.5 in /web_embedding/ng-flutter

Bumps [@angular/core](https://github.com/angular/angular/tree/HEAD/packages/core) from 20.3.16 to 21.1.5.
- [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/v21.1.5/packages/core)

---
updated-dependencies:
- dependency-name: "@angular/core"
  dependency-version: 21.1.5
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

web_embedding/ng-flutter/package.json

@@ -15,7 +15,7 @@
     "@angular/cdk": "^21.1.2",
     "@angular/common": "^21.1.1",
     "@angular/compiler": "^21.1.0",
-    "@angular/core": "^20.0.3",
+    "@angular/core": "^21.1.5",
     "@angular/forms": "^21.1.0",
     "@angular/material": "^21.1.1",
     "@angular/platform-browser": "^20.0.3",