fix: make the example workable

[ozbillwang]

Description

with original setting, nat gateway is disable, we have no chance to know why the ec2 instance can't be added to ECS cluster automatically, because when the ec2 instance started, it has a yum update job failed (no internet access, blocked and failed)

second, the default autoscaling group is set to 0 for desired size, it makes me crazy why I can't see it in ECS directly.

This PR fixed both problems

Motivation and Context

This PR fixed both problems described above.

Breaking Changes

No, it is example change.

How Has This Been Tested?

terraform init
terraform plan
terraform apply

[ozbillwang]

@antonbabenko

If nat gateway is disable as original code, we are very hard to troubleshooting the issue, because the ec2 instance has no keypair that you can use to ssh, and it is in private subnet (that means you need start up a jump box in public subnets)

So please think about the way when a newbie who need run your code, will be stuck there forever.

for me, even I worked on ECS for a while, it still takes me more than 1 hour to figure it out.

[antonbabenko]

Ok, no problems, I merged this one.

v2.2.0 has been just released.

[github-actions]

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