Update GitLab Pages to v1.2.1

What does this MR do?

A regression in GitLab Pages forced us to downgrade from v1.2.0 to v1.1.0: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/22277#note_107877334

The regression was fixed in gitlab-pages!114 (comment 108309032) . I've released a v1.2.1 with just that change relative to v1.2.0, so we should be able to upgrade Pages again.

I don't know whether we should pick this for %11.4 or not. WDYT @stanhu @jlenny ?

What are the relevant issue numbers?

Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/33422

Does this MR meet the acceptance criteria?

• [-] Changelog entry added, if necessary
• [-] Documentation created/updated
• [-] Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides