Bump dropbox-core-sdk from 3.0.5 to 3.1.5
Bump dropbox-core-sdk from 3.0.5 to 3.1.5

Bumps [dropbox-core-sdk](https://github.com/dropbox/dropbox-sdk-java) from 3.0.5 to 3.1.5.
- [Release notes](https://github.com/dropbox/dropbox-sdk-java/releases)
- [Changelog](https://github.com/dropbox/dropbox-sdk-java/blob/master/ChangeLog.txt)
- [Commits](https://github.com/dropbox/dropbox-sdk-java/compare/v3.0.5...v3.1.5)

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