[Security] Bump deep-extend from 0.4.2 to 0.6.0 in /terminus-ssh

Bumps [deep-extend](https://github.com/unclechu/node-deep-extend) from 0.4.2 to 0.6.0. **This update includes security fixes.**
- [Release notes](https://github.com/unclechu/node-deep-extend/releases)
- [Changelog](https://github.com/unclechu/node-deep-extend/blob/master/CHANGELOG.md)
- [Commits](https://github.com/unclechu/node-deep-extend/compare/v0.4.2...v0.6.0)