message: updated readme.md to package-2021-06-preview
diff: @@ -26,7 +26,7 @@ These are the global settings for the ServiceBus API.
  ``` yaml
  openapi-type: arm
  -tag: package-2018-01-preview
  +tag: package-2021-06-preview
  ```
  ### Tag: package-2021-01-preview
  