Bump version to 7.10.0

• Diff: https://gitlab.com/gitlab-org/gitlab-qa/compare/v7.9.3...2342dc399a2eb4b3d712d1e6675a4cec225a4fe7

• Release notes:

### Refactoring and updates

- !769 Cleanup env.rb env var method definitions

• Checklist before merging:

  • Diff link is up-to-date.
  • Based on the diff, lib/gitlab/qa/version.rb is updated, according to SemVer.
  • Release notes are accurate.

• Checklist after merging:

  • Update the release notes for the newly created tag.