Updated API from documentation release

Author: ct-sdks[bot]

api-specs/history/types/ModifiedBy.raml

@@ -9,7 +9,7 @@ properties:
   isPlatformClient:
     type: boolean
     description: |
-      `true` if the change was made using the Merchant Center or [ImpEx](https://impex.europe-west1.gcp.commercetools.com/).
+      `true` if the change was made using the Merchant Center.
   id?:
     type: string
     description: |

api-specs/history/types/Source.raml

@@ -10,4 +10,4 @@ description: Source of change for the resource.
 (enumDescriptions):
   MerchantCenter: The change was made through the Merchant Center.
   ApiClient: The change was made through an API Client.
-  ImpEx: The change was made through ImpEx.
+  ImpEx: The change was made through the now-decommissioned ImpEx tool.