Scale to 15 instances
Scale to 15 instances

 ## Summary
We hit our PaaS quotas when trying to scale to 20 instances, so we'll
stick to 15 and reduce the supplier-fe quota slightly.

 ## Ticket
https://trello.com/c/VJ9MdlsQ/310

alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws