Bump @angular/ssr from 18.2.20 to 18.2.21

Bumps [@angular/ssr](https://github.com/angular/angular-cli) from 18.2.20 to 18.2.21.
- [Release notes](https://github.com/angular/angular-cli/releases)
- [Changelog](https://github.com/angular/angular-cli/blob/main/CHANGELOG.md)
- [Commits](angular/angular-cli@18.2.20...18.2.21)

---
updated-dependencies:
- dependency-name: "@angular/ssr"
  dependency-version: 18.2.21
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]