Update changelog based on model updates

Author: aws-sdk-python-automation

.changes/next-release/api-change-workspaces-8764.json

@@ -0,0 +1,5 @@
+{
+  "type": "api-change",
+  "category": "``workspaces``",
+  "description": "Add StateMessage and ProgressPercentage fields to DescribeCustomWorkspaceImageImport API response."
+}