Bump the composer group across 1 directory with 2 updates

Bumps the composer group with 2 updates in the /admin directory: [symfony/process](https://github.com/symfony/process) and [phpoffice/phpspreadsheet](https://github.com/PHPOffice/PhpSpreadsheet).


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

Updates `phpoffice/phpspreadsheet` from 1.29.2 to 1.29.4
- [Release notes](https://github.com/PHPOffice/PhpSpreadsheet/releases)
- [Changelog](https://github.com/PHPOffice/PhpSpreadsheet/blob/1.29.4/CHANGELOG.md)
- [Commits](PHPOffice/PhpSpreadsheet@1.29.2...1.29.4)

---
updated-dependencies:
- dependency-name: symfony/process
  dependency-type: indirect
  dependency-group: composer
- dependency-name: phpoffice/phpspreadsheet
  dependency-type: indirect
  dependency-group: composer
...

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