Bump version to 1.26.0

Diff

https://gitlab.com/gitlab-org/ruby/gems/gitlab_quality-test_tooling/-/compare/1.25.0...jennli-bump-version-to-1.26.0

Checklist

• Diff link is up-to-date.
• Check the release notes: https://gitlab.com/api/v4/projects/gitlab-org%2Fruby%2Fgems%2Fgitlab_quality-test_tooling/repository/changelog?version=1.26.0
• Based on the diff and the release notes, version.rb is updated, according to SemVer.