[infra] Update GCP DB terraform to reflect backup region change

[daniel-goldstein]

I manually changed the Cloud SQL automated backups storage from the us multi-region to us-central1. There's no reason to store it in a multi-region and it's more expensive. What I didn't realize is that this configuration is actually owned by the terraform that we have managing the lifecycle of the database and other infra, so we need to update the terraform to reflect the desired (and current) state.

[daniel-goldstein]

On main, attempting to apply terraform says it wants to change the backup location from us-central1 to us, which is not what we want. With this change, applying terraform says everything is up to date ✅