Bump VERSION to 1.11.0

• Diff: https://gitlab.com/gitlab-org/gitlab-triage/compare/v1.10.1...5107e18

• Release notes:

### New features and features updates

- !164 Raise an error when any label in `actions.labels` doesn't exist.
- !168 Use the `not[labels]` API parameter for the `forbidden_labels` condition.

### Other changes (tooling, technical debt)

- !169 Include the gem release CI config.
- !170 Fix the `code_quality` job.

• Checklist before merging:

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

• Checklist after merging:

  • Update the release notes for the newly created tag.