Default configs do not conform to the new environment variable format

[Shayfiz]

Describe the bug
The newest release (v0.41.0) no longer supports the BASH-style environment variable expansion:

Note: Expansion of BASH-style environment variables, such as $FOO, is no longer be supported. Use ${FOO} or ${env:FOO} instead.

Steps to reproduce
Pull the latest image from the public ECR repository and start up the container with the following run command:
--config=/etc/ecs/ecs-amp-prometheus.yaml
Make sure that the env variables for AWS_PROMETHEUS_SCRAPING_ENDPOINT, AWS_PROMETHEUS_ENDPOINT, and AWS_REGION are set.

I did this within an ECS task definition.

What did you expect to see?
I expected the container to start up successfully.

What did you see instead?
I got the following error in my ECS logs;
Error: failed to build pipelines: failed to create "prometheusremotewrite" exporter for data type "metrics": invalid endpoint

Environment
AWS_PROMETHEUS_SCRAPING_ENDPOINT = "0.0.0.0:8000"
AWS_PROMETHEUS_ENDPOINT = The prometeheus endpoint of my prometheus workspace
AWS_REGION = "eu-west-2"

Additional context
The way that I have currently fixed it is to create my own image, which uses a modified version of ecs-amp-prometheus.yaml. Within that, all environment variable references were replaced with the new format, e.g.: $AWS_REGION to "${AWS_REGION}". The container starts up successfully when that custom image is used.