docs/aws: `aws_alb` name parameter is now documented as a Required

field

The validation rules are also included in the documentation

Fixes #8561

website/source/docs/providers/aws/r/alb.html.markdown

@@ -37,7 +37,8 @@ resource "aws_alb" "test" {
 
 The following arguments are supported:
 
-* `name` - (Optional) The name of the ALB. By default generated by Terraform.
+* `name` - (Required) The name of the ALB. This name must be unique within your AWS account, can have a maximum of 
+32 characters, must contain only alphanumeric characters or hyphens, and must not begin or end with a hyphen.
 * `internal` - (Optional) If true, the ALB will be internal.
 * `security_groups` - (Optional) A list of security group IDs to assign to the ELB.
 * `access_logs` - (Optional) An Access Logs block. Access Logs documented below.