Upgrade prod sumo DB to 5.7 and downsize the DB instance

[rvaralda]

SE-1718 Updates to sumo prod RDS

• db.m5.4xlarge -> db.m5.2xlarge
• Upgrade MySQL from 5.6 to 5.7

[rvaralda]

$ tf plan -refresh=false

Terraform used the selected providers to generate the following execution plan.
Resource actions are indicated with the following symbols:
  ~ update in-place

Terraform will perform the following actions:

  # module.mysql-prod.aws_db_instance.sumo_rds will be updated in-place
  ~ resource "aws_db_instance" "sumo_rds" {
      ~ engine_version                        = "5.6.51" -> "5.7"
        id                                    = "sumo"
      ~ instance_class                        = "db.m5.4xlarge" -> "db.m5.2xlarge"
        name                                  = "sumo_prod"
        tags                                  = {
            "Environment" = "prod"
            "Project"     = "sumo"
            "Region"      = "us-west-2"
            "Stack"       = "SUMO-prod"
            "Terraform"   = "true"
        }
        # (48 unchanged attributes hidden)
    }

Plan: 0 to add, 1 to change, 0 to destroy.