amended sustainability docs to correctly reference nightly RDS instan…

…ce shutdowns outside of production (#5774)

source/user-guide/sustainability.html.md.erb

@@ -1,7 +1,7 @@
 ---
 owner_slack: "#modernisation-platform"
 title: Sustainability
-last_reviewed_on: 2023-11-10
+last_reviewed_on: 2023-12-11
 review_in: 6 months
 ---
 
@@ -24,11 +24,10 @@ You can view our open and closed issues on sustainability [here](https://github.
 - We are paperless
 - We are collaborating and feeding in to wider department and organisation sustainability objectives
 - Switched from using Python to Go programming language which consumes less energy
-- Shut down all non production EC2 instances by default at night
+- Shut down all non production EC2 & RDS instances by default at night
 
 ## What are we planning to do?
 
-- Shut down all non production RDS instances by default at night
 - Start reporting on Cloud usage
 - Work with other hosting teams to reuse and consolidate tools, infrastructure and teams where we can
 - Create a central billing dashboard to help monitor usage and promote efficiency