[Listen Notes] Transition to Graviton-Based EC2 instances

Today marks the completion of our long-term project (> 2 years) to replace all Listen Notes AWS EC2 instances from Intel CPUs to Graviton-based CPUs.

The final servers running on r6i instances have now been upgraded to r8g instances.

We are very happy with the results: the new instances are not only cheaper but also offer better overall performance!