[BUG] AWS Backup doesn't work when Encryption is configured on EFS nodes

[dgoodellrhy]

Describe the bug
When creating an EFS volume with a KMS key encryption, AWS Backup fails

To Reproduce

module "app_efs" {
  source  = "rhythmictech/efs-filesystem/aws"
  version = "~> 0.1.1"

  name                    = "${var.env}-efs"
  allowed_security_groups = [aws_security_group.allow_app_efs_access.id]
  enable_backups          = true
  provisioned_throughput  = var.efs_provisioned_throughput
  subnets                 = data.terraform_remote_state.network.outputs.private_subnets
  throughput_mode         = var.efs_throughput_mode
  vpc_id                  = local.vpc_id
  additional_tags = ""
}

Expected behavior
creating an EFS volume using encryption without specifying a DMS key allows EFS backups when they are configured

Screenshots

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Additional context