fix(documentation): autovacuum value

[jeremychauvet]

Description of changes: This MR aims to change the value of autovacuum parameter. You can see on the following picture allowed values:

This MR will also prevent the following continuous drift on Terraform stacks:

# module.xxxx.rds.aws_db_parameter_group.postgres will be updated in-place
  ~ resource "aws_db_parameter_group" "postgres" {
        id          = "xxxxx"
        name        = "xxxxx"
      - parameter {
          - apply_method = "immediate" -> null
          - name         = "autovacuum" -> null
          - value        = "0" -> null
        }
      + parameter {
          + apply_method = "immediate"
          + name         = "autovacuum"
          + value        = "Off"
        }
    }

[LavanyaGunreddi]

Hi, sorry for the delay. The doc has been modified and the change will reflect in the next refresh cycle. Thanks!