Update the module documentation.

README.md

@@ -260,7 +260,6 @@ terraform destroy
 | ami\_owners | The list of owners used to select the AMI of Gitlab runner agent instances. | `list(string)` | <pre>[<br> "amazon"<br>]</pre> | no |
 | arn\_format | ARN format to be used. May be changed to support deployment in GovCloud/China regions. | `string` | `"arn:aws"` | no |
 | aws\_region | AWS region. | `string` | n/a | yes |
-| aws\_zone | AWS availability zone (typically 'a', 'b', or 'c'). | `string` | `"a"` | no |
 | cache\_bucket | Configuration to control the creation of the cache bucket. By default the bucket will be created and used as shared cache. To use the same cache across multiple runners disable the creation of the cache and provide a policy and bucket name. See the public runner example for more details. | `map` | <pre>{<br> "bucket": "",<br> "create": true,<br> "policy": ""<br>}</pre> | no |
 | cache\_bucket\_name\_include\_account\_id | Boolean to add current account ID to cache bucket name. | `bool` | `true` | no |
 | cache\_bucket\_prefix | Prefix for s3 cache bucket name. | `string` | `""` | no |
@@ -362,4 +361,4 @@ terraform destroy
 | runner\_role\_name | Name of the role used for the docker machine runners. |
 | runner\_sg\_id | ID of the security group attached to the docker machine runners. |
 
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