Update slim/slim requirement from ^3.12.1 to ^4.3.0
Update slim/slim requirement from ^3.12.1 to ^4.3.0

Updates the requirements on [slim/slim](https://github.com/slimphp/Slim) to permit the latest version.
- [Release notes](https://github.com/slimphp/Slim/releases)
- [Changelog](https://github.com/slimphp/Slim/blob/4.x/CHANGELOG.md)
- [Commits](https://github.com/slimphp/Slim/compare/3.12.1...4.3.0)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
nekofar/slim-rest-crud