Remove doc about stacks in AWS
Remove doc about stacks in AWS

This manual is quite high-level and doesn't seem to contain much
actionable content: perhaps I'm wrong, but I can't see people on
GOV.UK using this manual to deploy an alternative infra stack. We
can remove the manual to try and consolidate our docs on AWS.

alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs