provider/aws: Documentation fixes for aws_ami (#13694)

* provider/aws: Documentation fixes for aws_ami

Fixes: #13685

* Update ami.html.markdown

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

@@ -81,12 +81,12 @@ Nested `ebs_block_device` blocks have the following structure:
   as the selected snapshot.
 * `volume_type` - (Optional) The type of EBS volume to create. Can be one of "standard" (the
   default), "io1" or "gp2".
-* `encrypted` - (Optional) Specifies whether the destination snapshots of the copied image should be encrypted.
-The default CMK for EBS is used unless a non-default AWS Key Management Service (AWS KMS) CMK is specified with KmsKeyId.
 * `kms_key_id` - (Optional) The full ARN of the AWS Key Management Service (AWS KMS) CMK to use when encrypting the snapshots of
 an image during a copy operation. This parameter is only required if you want to use a non-default CMK;
 if this parameter is not specified, the default CMK for EBS is used
 
+~> **Note:** You can specify `encrypted` or `snapshot_id` but not both.
+
 Nested `ephemeral_block_device` blocks have the following structure:
 
 * `device_name` - (Required) The path at which the device is exposed to created instances.