Update openfisca-core requirement from <27,>=26 to >=26,<28
Update openfisca-core requirement from <27,>=26 to >=26,<28

Updates the requirements on [openfisca-core](https://github.com/openfisca/openfisca-core) to permit the latest version.
- [Release notes](https://github.com/openfisca/openfisca-core/releases)
- [Changelog](https://github.com/openfisca/openfisca-core/blob/master/CHANGELOG.md)
- [Commits](https://github.com/openfisca/openfisca-core/compare/26.0.0...27.0.0)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
openfisca/openfisca-tunisia,openfisca/openfisca-tunisia