Cleanup Pages Configuration

Due to not having sent a notification out soon enough, we need to keep the proxy around a little bit longer than initially thought.

Utilize this story as a blocker to prevent the removal of the azure proxy for pages beforehand.

Keep track of the following MR regarding notification: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21163

The goal would be to prevent removal of the proxy prior to the 22nd of October.

cc: @gl-infra

Cleanup of Pages

• Modify DNS as necessary
• Grab a list of projects still using the old DNS record, send to support such that they can send notification
• Remove the pages proxy