Update GitLab Pages to v0.6.0

What does this MR do?

Update GitLab Pages to v0.6.0 - release issue: https://gitlab.com/gitlab-org/gitlab-pages/issues/85

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Essential prerequisite of https://gitlab.com/gitlab-org/omnibus-gitlab/issues/2747 https://gitlab.com/gitlab-org/gitlab-ce/issues/34102

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Review
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Related to #34102 https://gitlab.com/gitlab-org/gitlab-pages/issues/85