Bump to version 7.7.0

• Diff: https://gitlab.com/gitlab-org/gitlab-qa/compare/v7.6.0...34884c3c6743fd3d4e3358dd6c1e86e81a66ba3a

• Release notes:

### New scenarios and scenario updates

- !734 Integrate AWS S3 for object storage testing
- !715 Update Gitaly Cluster config

### Other changes (CI, backstage)

- !732 Remove unused scenarios to optimise pipeline
- !730 Use a dedicated project access token for leaving comments on upstream commits
- !728 Use allure report job definition from common-pipelines
- !717 Adding a job for execution of large MR's

• 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.