Update endpoints model

Author: AWS SDK for Go v2 automation user

codegen/smithy-aws-go-codegen/src/main/resources/software/amazon/smithy/aws/go/codegen/endpoints.json

@@ -5146,6 +5146,7 @@
           "ap-south-1" : { },
           "ap-southeast-1" : { },
           "ap-southeast-2" : { },
+          "ap-southeast-3" : { },
           "ca-central-1" : { },
           "eu-central-1" : { },
           "eu-north-1" : { },