Changed `attribute` argument to be optional.
Changed `attribute` argument to be optional.

Changed the `attribute` argument of the resource to be optional vs.
required.

ClementCunin/terraform-provider-aws,ashinohara/terraform-provider-aws,ClementCunin/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,Ninir/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,ashinohara/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,kjmkznr/terraform-provider-aws,ClementCunin/terraform-provider-aws,terraform-providers/terraform-provider-aws,nbaztec/terraform-provider-aws,nbaztec/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,terraform-providers/terraform-provider-aws,ClementCunin/terraform-provider-aws,nbaztec/terraform-provider-aws,Ninir/terraform-provider-aws,kjmkznr/terraform-provider-aws,nbaztec/terraform-provider-aws,kjmkznr/terraform-provider-aws,Ninir/terraform-provider-aws,terraform-providers/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,Ninir/terraform-provider-aws,ashinohara/terraform-provider-aws,ashinohara/terraform-provider-aws