Bump symfony/security-http from 6.4.14 to 6.4.15 in /webapp

Bumps [symfony/security-http](https://github.com/symfony/security-http) from 6.4.14 to 6.4.15.
- [Release notes](https://github.com/symfony/security-http/releases)
- [Changelog](https://github.com/symfony/security-http/blob/7.1/CHANGELOG.md)
- [Commits](symfony/security-http@v6.4.14...v6.4.15)

---
updated-dependencies:
- dependency-name: symfony/security-http
  dependency-type: indirect
...

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

Author: dependabot[bot]