Add documentation on removing Federalist sites

[amirbey]

trafficstars

User Story

A user should know what steps to take to remove their site (production and development) from Federalist.

Background (Optional)

Acceptance Criteria

• [ ] write documentation on how an operator removes a site from Federalist
• [ ] Change made live via cloud-gov/cg-site

After evaluating, edit this part:

Level of effort - <low/medium/high>

Implementation outline (if higher than "low" effort):

• [ ] <TODO>

[Ephraim-G]

Does any documentation currently exist pertaining to this issue?