Bump symfony/security-guard from 5.2.1 to 5.2.8 in /app (#26)

Bumps [symfony/security-guard](https://github.com/symfony/security-guard) from 5.2.1 to 5.2.8.
- [Release notes](https://github.com/symfony/security-guard/releases)
- [Changelog](https://github.com/symfony/security-guard/blob/5.x/CHANGELOG.md)
- [Commits](symfony/security-guard@v5.2.1...v5.2.8)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>