provider/aws: Make 'stage_name' required in api_gateway_deployment (#6797)

When stage_name is not passed to the resource
aws_api_gateway_deployment a terraform apply will fail. This is
because the stage_name is required and not optional.

builtin/providers/aws/resource_aws_api_gateway_deployment.go

@@ -28,7 +28,7 @@ func resourceAwsApiGatewayDeployment() *schema.Resource {
 
 			"stage_name": &schema.Schema{
 				Type:     schema.TypeString,
-				Optional: true,
+				Required: true,
 				ForceNew: true,
 			},
 

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

@@ -50,7 +50,7 @@ resource "aws_api_gateway_deployment" "MyDemoDeployment" {
 The following arguments are supported:
 
 * `rest_api_id` - (Required) The ID of the associated REST API
-* `stage_name` - (Optional) The name of the stage
+* `stage_name` - (Required) The name of the stage
 * `description` - (Optional) The description of the deployment
 * `stage_description` - (Optional) The description of the stage
 * `variables` - (Optional) A map that defines variables for the stage