fix(ecs): IAM role ARN must not specific region. (#3755)

fixes #3733

Author: nija-at

packages/@aws-cdk/aws-ecs/lib/base/base-service.ts

@@ -328,6 +328,7 @@ export abstract class BaseService extends Resource
   private makeAutoScalingRole(): iam.IRole {
     // Use a Service Linked Role.
     return iam.Role.fromRoleArn(this, 'ScalingRole', Stack.of(this).formatArn({
+      region: '',
       service: 'iam',
       resource: 'role/aws-service-role/ecs.application-autoscaling.amazonaws.com',
       resourceName: 'AWSServiceRoleForApplicationAutoScaling_ECSService',

packages/@aws-cdk/aws-ecs/test/fargate/integ.lb-awsvpc-nw.expected.json

@@ -514,11 +514,7 @@
               {
                 "Ref": "AWS::Partition"
               },
-              ":iam:",
-              {
-                "Ref": "AWS::Region"
-              },
-              ":",
+              ":iam::",
               {
                 "Ref": "AWS::AccountId"
               },