chore: add info to changelog

Author: Justintime50

CHANGELOG.md

@@ -6,6 +6,7 @@
 - Fixes error parsing
   - Allows for alternative format of `errors` field
   - Corrects available properties of an `EasyPostError` and `ApiError` (`code` and `field` removed from `EasyPostError`, `message` unfurled and explicitly added to `ApiError`)
+  - Removes unused `Error` model
 - Corrects the HTTP verb for updating a brand from `GET` to `PATCH`
 - Removes the deprecated `create_list` tracker endpoint function as it is no longer available via API