Bump version to 6.11.0

• Diff: https://gitlab.com/gitlab-org/gitlab-qa/compare/v6.10.1...c47ddec57f59425e5a794a355adde5e61e447b3b

• Release notes:

### Fixes

- !586 Ensure title is truncated when creating new E2E failure issues

### Doc changes

- !581 Fix typo in running specific orchestrated tests doc

### Other changes (CI, backstage)

- !587 Add debugging to identify a problem that happens on CI

• 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:

  • Create a tag for the new release version.