Update the README

Now that we use `terraform-docs` to populate information about the
template's variables we do not need a manually managed table with that
information in the README.

README.md

@@ -104,20 +104,8 @@ source_profile = build-skeleton-packer
 role_session_name = example
 ```
 
-The [Packer template](variables.pkr.hcl) defines a number of variables:
-
-| Name | Description | Type | Default | Required |
-|------|-------------|------|---------|:--------:|
-| ami\_regions | The list of AWS regions to copy the AMI to once it has been created. Example: ["us-east-1"] | `list(string)` | `[]` | no |
-| build\_region | The region in which to retrieve the base AMI from and build the new AMI. | `string` | `"us-east-1"` | no |
-| build\_region\_kms | The ID or ARN of the KMS key to use for AMI encryption. | `string` | `"alias/cool-amis"` | no |
-| is\_prerelease | The pre-release status to use for the tags applied to the created AMI. | `bool` | `false` | no |
-| region\_kms\_keys | A map of regions to copy the created AMI to and the KMS keys to use for encryption in that region. The keys for this map must match the values provided to the aws\_regions variable. Example: {"us-east-1": "alias/example-kms"} | `map(string)` | `{}` | no |
-| release\_tag | The GitHub release tag to use for the tags applied to the created AMI. | `string` | `""` | no |
-| release\_url | The GitHub release URL to use for the tags applied to the created AMI. | `string` | `""` | no |
-| skip\_create\_ami | Indicate if Packer should not create the AMI. | `bool` | `false` | no |
-
-Changing these defaults can be done through a `.pkrvars.hcl` file:
+This Packer template defines a number of variables whose defaults can be changed
+through a `.pkrvars.hcl` file:
 
 ```hcl
 build_region = "us-east-2"