[terraform] Increase keyserver primary ecs task resources

Summary:
Noticed that keyserver initial setup is cpu intensive which at time triggers fargate autoscaling

Depends on D12558

Test Plan: successful terraform apply and max cpu usage is now around ~50-60% instead of ~80%

Reviewers: bartek, varun

Reviewed By: bartek

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D12559