Update readme.python.md (Azure#22568)

Author: Wzb123456789

specification/appplatform/resource-manager/readme.python.md

@@ -20,6 +20,7 @@ Generate all API versions currently shipped for this package
 
 ```yaml $(python)
 multiapi: true
+default-api-version: "2022-12-01"
 clear-output-folder: true
 batch:
   - tag: package-2022-12