Default to us-east-1 region for AWS SDK v2

What does this MR do?

Previously the Minio SDK defaulted to us-east-1, so use this as the default to preserve backwards compatability.

Why was this MR needed?

Leaving out BucketLocation would cause an error.

What's the best way to test this MR?

Use an S3 bucket:

 [runners.cache]
    Type = "s3"
    [runners.cache.s3]
    BucketName = "YOUR-BUCKET"

What are the relevant issue numbers?

!4987 (comment 2168110227)