Bump ava from 3.12.1 to 3.15.0

Bumps [ava](https://github.com/avajs/ava) from 3.12.1 to 3.15.0.
- [Release notes](https://github.com/avajs/ava/releases)
- [Commits](avajs/ava@v3.12.1...v3.15.0)

---
updated-dependencies:
- dependency-name: ava
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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