Bump pygments from 1.6 to 2.7.4 in /installer

Bumps [pygments](https://github.com/pygments/pygments) from 1.6 to 2.7.4.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](https://github.com/pygments/pygments/compare/1.6...2.7.4)

---
updated-dependencies:
- dependency-name: pygments
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
2 files changed