Remove explicit private ACLs, since ACLs are disallowed by default

[agerbens]

Fixes #8

We'll probably want to make a 3.0.0 tag so as not to affect anyone on 2.

[dragonfleas]

I don't mind doing a minor tag release for this. I don't think a major is necessary because it's not a breaking change.

[agerbens]

I think it'll impact anybody that made a bucket with ACLs enabled (the old default). Suddenly having them removed would cause a change on the next terraform apply, wouldn't it?

Though, yeah, I'm not really sure that would count as a breaking change.

Another possible solution for this would be to just enable ACLs and explicitly have a private ACL, like this snippet taken from the linked issue.

resource "aws_s3_bucket" "example" {
  bucket = "my-tf-test-bucket"
}

resource "aws_s3_bucket_ownership_controls" "example" {
  bucket = aws_s3_bucket.example.id
  rule {
    object_ownership = "BucketOwnerPreferred"
  }
}

resource "aws_s3_bucket_acl" "example" {
  depends_on = [aws_s3_bucket_ownership_controls.example]

  bucket = aws_s3_bucket.example.id
  acl    = "private"
}

I think that would make it closer to the pre-April 2023 settings.
Do you have a preference?

[dragonfleas]

I don't necessarily have a strong preference either way since we are blocking public access, I think sticking with defaults that AWS recommends unless required otherwise is wise.

I'm pretty sure we had private ACLs only as a security measure recommended by tfsec anyways.