Remove manuals_publisher_production database

[chrisroos]

The Manuals Publisher app uses the govuk_content_production Mongo database in production and govuk_content_development in development. However, there is a manuals_publisher_production Mongo database which is also dumped and restored via the data replication scripts to manuals_publisher_development.

I assume the manuals_publisher_production database is no longer used in which case it would be helpful to remove it; at least from the data replication scripts. It's particularly confusing, because it's easy to assume that the app is using the manuals_publisher_development database locally.

This was originally added as a card in Trello by @floehopper. I've moved it because we've agreed to use GitHub issues instead of Trello.

[floehopper]

Based on #893, we might want to consider re-purposing the existing manuals_publisher_production database rather than removing it.