Update version to 8.11.0

Diff

https://gitlab.com/gitlab-org/gitlab-qa/compare/v8.10.2...add619aada56f717d7aa4bf0e9d6e482ff977211

Release notes:

New scenarios and scenario updates

• Add importers scenario type (!1078 - merged)

Other changes (CI, backstage)

• update integrations docs to reflect running aga... (!1072 - merged)

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.