Update mongodb requirement from ^3.6.6 to ^3.6.9
Update mongodb requirement from ^3.6.6 to ^3.6.9

Updates the requirements on [mongodb](https://github.com/mongodb/node-mongodb-native) to permit the latest version.
- [Release notes](https://github.com/mongodb/node-mongodb-native/releases)
- [Changelog](https://github.com/mongodb/node-mongodb-native/blob/3.6/CHANGES_3.0.0.md)
- [Commits](https://github.com/mongodb/node-mongodb-native/compare/v3.6.6...v3.6.9)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
ioBroker/ioBroker.node-red,ioBroker/ioBroker.node-red