update log delivery example with working ACL

the acl in this document doesn't match what is required, now it does: https://docs.aws.amazon.com/AmazonS3/latest/userguide/enable-server-access-logging.html#grant-log-delivery-permissions-general

website/docs/r/s3_bucket.html.markdown

@@ -327,7 +327,7 @@ resource "aws_s3_bucket" "bucket" {
 
   grant {
     type        = "Group"
-    permissions = ["READ", "WRITE"]
+    permissions = ["READ_ACP", "WRITE"]
     uri         = "http://acs.amazonaws.com/groups/s3/LogDelivery"
   }
 }