Merge pull request #430 from EasyPost/v4.6.0-changelog

docs: update CHANGELOG

Author: Justintime50

CHANGELOG.md

@@ -1,9 +1,11 @@
 # CHANGELOG
 
-## v4.6.0 (Next Release)
+## v4.6.0 (2023-04-18)
 
 - Adds `GetNextPage` function to each service which retrieves the next page of a collection when the `has_more` key is present in the response (eg: `Client.Address.GetNextPage(addressCollection)`)
+- Adds `RetrieveCarrierMetadata` via `myClient.Beta.CarrierMetadata`
 - Fixes the type of `RequestBody` from Dictionary to String in Payload class
+- Fixes a deserialization bug when an error.message from the API was returned as an object instead of a string
 
 ## v4.5.0 (2023-03-22)