update cloud-gov/pages documentation with new app names

[amirbey]

User Story

Background (Optional)

When the names of the apps get renamed update the app names in the Pages documentation ie: federalist-proxy.app.cloud.gov -> pages-proxy.app.cloud.gov

Acceptance Criteria

• [ ] <TODO>
• [ ] Change made live via <TODO>.

After evaluating, edit this part:

Level of effort - <low/medium/high>

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

• [ ] <TODO>