Bump flat and nightwatch

Bumps [flat](https://github.com/hughsk/flat) to 5.0.2 and updates ancestor dependency [nightwatch](https://github.com/nightwatchjs/nightwatch). These dependencies need to be updated together.


Updates `flat` from 4.1.1 to 5.0.2
- [Release notes](https://github.com/hughsk/flat/releases)
- [Commits](hughsk/flat@4.1.1...5.0.2)

Updates `nightwatch` from 1.7.13 to 2.6.3
- [Release notes](https://github.com/nightwatchjs/nightwatch/releases)
- [Commits](nightwatchjs/nightwatch@v1.7.13...v2.6.3)

---
updated-dependencies:
- dependency-name: flat
  dependency-type: indirect
- dependency-name: nightwatch
  dependency-type: direct:development
...

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

Author: dependabot[bot]