Change SSE for S3 bucket from "aws:kms" to "AES256" so that cross

account decryption of files can take place.

terraform/deployments/opensearch/s3.tf

@@ -27,7 +27,7 @@ resource "aws_s3_bucket_server_side_encryption_configuration" "opensearch_snapsh
   bucket = aws_s3_bucket.opensearch_snapshot.id
   rule {
     apply_server_side_encryption_by_default {
-      sse_algorithm = "aws:kms"
+      sse_algorithm = "AES256"
     }
   }
 }