docs/resource/aws_emr_cluster: Adjust wording that multi-master only requires public subnets to have public IP on launch
docs/resource/aws_emr_cluster: Adjust wording that multi-master only requires public subnets to have public IP on launch

Reference: https://github.com/terraform-providers/terraform-provider-aws/pull/9235#pullrequestreview-257932291

kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws