fix: managed_policy_arns deprecated

[scottschreckengaust]

Update the deprecation warning:

│ Warning: Argument is deprecated
│ 
│   with module.genai_doc_ingestion.module.document_ingestion.aws_iam_role.ingestion_api_datasource,
│   on .terraform/modules/genai_doc_ingestion/modules/document-ingestion/iam.tf line 44, in resource "aws_iam_role" "ingestion_api_datasource":
│   44:   managed_policy_arns = [
│   45:     "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole",
│   46:     "arn:aws:iam::aws:policy/AmazonEventBridgeFullAccess",
│   47:   ]
│ 
│ The managed_policy_arns argument is deprecated. Use the aws_iam_role_policy_attachments_exclusive resource instead.