Update CI release task to upload with AWS CLI

What does this MR do?

The Travis CI artifacts tool does not support concurrent multipart uploads, so our 15 GB uploads take around 20 minutes. The AWS CLI tool is optimized for faster transfers.

Switch to saas-linux-medium-amd64 runner since having a beefier runner seems to have dropped the job time from 50 minutes to 15.

Why was this MR needed?

release s3 CI job was taking 50 minutes.

What's the best way to test this MR?

See https://gitlab.com/gitlab-org/gitlab-runner/-/jobs/8167071140.

What are the relevant issue numbers?

No issue created.