Remove absent env sync tasks for production db_admin
Remove absent env sync tasks for production db_admin

These tasks were marked absent as part of the migration from shared RDS
to a RDS instance for each application. As Puppet has now run on the
target machines, these can be removed.

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet