Enable IPv6 for Pages for GitLab.com

Related to Support IPv6 for Pages hosting. (gitlab-com/gl-infra/reliability#10406), which may resolve this issue at the same time.

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We have a customer asking if we can support IPv6 for Pages for GitLab.com.

#214438 (closed)

Can we enable?

We need to:

• Create a production change request for adding IPv6 address to pages
• Update in documentation with the new IPv6 address