Bump octokit from 2.1.0 to 3.1.2

Bumps [octokit](https://github.com/octokit/octokit.js) from 2.1.0 to 3.1.2.
- [Release notes](https://github.com/octokit/octokit.js/releases)
- [Commits](octokit/octokit.js@v2.1.0...v3.1.2)

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

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

Author: dependabot[bot]