Update amazon-chroot.html.md.erb

use content of partial to be able to autodoc :D

website/source/docs/builders/amazon-chroot.html.md.erb

@@ -159,7 +159,13 @@ each category, the available configuration keys are alphabetized.
 -   `insecure_skip_tls_verify` (boolean) - This allows skipping TLS
     verification of the AWS EC2 endpoint. The default is `false`.
 
-<%= partial "partials/builders/aws-common-opional-fields" %>
+-   `kms_key_id` (string) - ID, alias or ARN of the KMS key to use for boot
+    volume encryption. This only applies to the main `region`, other regions
+    where the AMI will be copied will be encrypted by the default EBS KMS key.
+    For valid formats see *KmsKeyId* in the [AWS API docs -
+    CopyImage](https://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_CopyImage.html).
+    This field is validated by Packer, when using an alias, you will have to
+    prefix `kms_key_id` with `alias/`.
 
 -   `from_scratch` (boolean) - Build a new volume instead of starting from an
     existing AMI root volume snapshot. Default `false`. If `true`, `source_ami`