message: update attestation to 2020-10-01
diff: @@ -26,7 +26,7 @@ These are the global settings for the Attestation API.
  ``` yaml
  openapi-type: arm
  -tag: package-2018-09-01
  +tag: package-2020-10-01
  ```
  ### Tag: package-2018-09-01
  