Docs: GitLab Pivotal Tile no longer available

Details

As per https://docs.pivotal.io/partners/gitlab/index.html, the Gitlab Pivotal tile is no longer available, so the GitLab Pivotal Tile Doc should be edited to show that it is deprecated, or the doc should be deleted (along with any links to it).

New doc or update?

• New documentation
• Update existing documentation

Docs Team

• Add the correct labels
• Add the correct milestone