Update database_cleaner requirement from ~> 1.6 to ~> 2.0
Update database_cleaner requirement from ~> 1.6 to ~> 2.0

Updates the requirements on [database_cleaner](https://github.com/DatabaseCleaner/database_cleaner) to permit the latest version.
- [Release notes](https://github.com/DatabaseCleaner/database_cleaner/releases)
- [Changelog](https://github.com/DatabaseCleaner/database_cleaner/blob/main/History.rdoc)
- [Commits](https://github.com/DatabaseCleaner/database_cleaner/compare/v1.6.0...v2.0.1)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
doorkeeper-gem/doorkeeper,doorkeeper-gem/doorkeeper,doorkeeper-gem/doorkeeper