[ECS Service Connect] [change app protocol]: allow changing of app protocol after creation

### Community Note

* Please vote on this issue by adding a 👍 [reaction](https://blog.github.com/2016-03-10-add-reactions-to-pull-requests-issues-and-comments/) to the original issue to help the community and maintainers prioritize this request
* Please do not leave "+1" or "me too" comments, they generate extra noise for issue followers and do not help prioritize the request
* If you are interested in working on this issue or have submitted a pull request, please leave a comment

**Tell us about your request**

When setting up Service Connect you can optionally set a field for appProtocol in the task definition, https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task_definition_parameters.html

It seems that this field is not editable after creation of the service, if you attempt to change it you get an error such as:

```
There was an error updating Service.
The following config cannot be changed for a SC service. Previous config: ScServiceStableConfig(applicationProtocol=null, transportProtocol=tcp, ecsServiceArn=arn:aws:ecs:us-east-1:1231313131313:service/sc-fargate/nginx1), current config: ScServiceStableConfig(applicationProtocol=http2, transportProtocol=tcp, ecsServiceArn=arn:aws:ecs:us-east-1:1231313131313:service/sc-fargate/nginx1)
```

This field should be modifiable without having to recreate the service.

**Which service(s) is this request for?**

ECS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**

If this field needs to be modified, downtime is required to do so as the service needs to be recreated. There are many reasons it may need modification. The most common is probably that it defaults to "tcp", but when set to "tcp" you can not adjust the timeout settings for the port.

**Are you currently working around this issue?**

Recreate the service