Update endpoints model

Author: aws-sdk-python-automation

awscli/botocore/data/endpoints.json

@@ -16974,6 +16974,7 @@
           "ap-southeast-3" : { },
           "ap-southeast-4" : { },
           "ap-southeast-5" : { },
+          "ap-southeast-6" : { },
           "ap-southeast-7" : { },
           "ca-central-1" : {
             "variants" : [ {