Remove the 2019Exemplar Fargate service from cluster definition

[MikeTheCanuck]

While we worked to validate that #238 is in fact a working CD pipeline for Fargate-based contianers, we added a temporary definition for the 2019 Exemplar.

However, since this wasn't deploying any better, and because we're still highly confident this is a valid configuration for container deploys to Fargate, I've elected to merge that configuration and continue to iterate on it for other orthogonal improvements.

Thus we'll need to remove references to this 2019Exemplar service, once we've completed the troubleshooting work:

• remove "2019Exemplar" stanza from master.yaml
• remove testing/2019-examplar ECR repo