Bump debug and phantomjs-prebuilt

Bumps [debug](https://github.com/debug-js/debug) and [phantomjs-prebuilt](https://github.com/Medium/phantomjs). These dependencies needed to be updated together.

Updates `debug` from 0.7.4 to 2.6.9
- [Release notes](https://github.com/debug-js/debug/releases)
- [Changelog](https://github.com/debug-js/debug/blob/2.6.9/CHANGELOG.md)
- [Commits](debug-js/debug@0.7.4...2.6.9)

Updates `phantomjs-prebuilt` from 2.1.14 to 2.1.16
- [Release notes](https://github.com/Medium/phantomjs/releases)
- [Commits](https://github.com/Medium/phantomjs/commits)

---
updated-dependencies:
- dependency-name: debug
  dependency-type: indirect
- dependency-name: phantomjs-prebuilt
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]