docs: trim IAM role setup

Co-authored-by: open-swe[bot] <open-swe@users.noreply.github.com>

src/langsmith/data-export-destinations.mdx

@@ -398,30 +398,6 @@ resource "aws_iam_role" "langsmith_bulk_export" {
 
 Replace the subject ID placeholders with the values from the selected region. Add the optional permissions from [AWS S3 permissions](#aws-s3-permissions) if you want LangSmith to clean up test files, verify file sizes, or abort multipart uploads.
 
-### Create a destination with the role
-
-After you create the AWS role, pass its ARN as `aws_role_arn` instead of providing `credentials`:
-
-```bash
-curl --request POST \
-  --url 'https://api.smith.langchain.com/api/v1/bulk-exports/destinations' \
-  --header 'Content-Type: application/json' \
-  --header 'X-API-Key: YOUR_API_KEY' \
-  --header 'X-Tenant-Id: YOUR_WORKSPACE_ID' \
-  --data '{
-    "destination_type": "s3",
-    "display_name": "My AWS S3 Destination",
-    "config": {
-      "bucket_name": "YOUR_BUCKET_NAME",
-      "prefix": "data_exports",
-      "region": "YOUR_AWS_REGION"
-    },
-    "aws_role_arn": "arn:aws:iam::YOUR_AWS_ACCOUNT_ID:role/langsmith-bulk-export"
-  }'
-```
-
-LangSmith validates the role with a test write before saving the destination. The request fails with `400` if the trust policy or S3 permissions are insufficient.
-
 ## Switch authentication mode
 
 Switch an existing destination between static credentials and [AWS IAM role assumption](#authenticate-with-an-aws-iam-role) without recreating it. Use `PATCH /api/v1/bulk-exports/destinations/{destination_id}`.