Update Hashicorp AWS assume role auth docs (apache#39287)

docs/apache-airflow-providers-hashicorp/secrets-backends/hashicorp-vault.rst

@@ -220,14 +220,15 @@ Add "verify": "absolute path to ca-certificate file"
 Vault authentication with AWS Assume Role STS
 """""""""""""""""""""""""""""""""""""""""""""
 
-Add parameter "role_arn": "The AWS ARN of the role to assume"
+Add parameter "assume_role_kwargs": "The AWS STS assume role auth parameter dict"
+
+For more details, please refer to the AWS Assume Role Authentication documentation: https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/sts/client/assume_role.html
 
 .. code-block:: ini
 
     [secrets]
     backend = airflow.providers.hashicorp.secrets.vault.VaultBackend
-    backend_kwargs = {"connections_path": "airflow-connections", "variables_path": null, "mount_point": "airflow", "url": "http://127.0.0.1:8200", "auth_type": "aws_iam", "role_arn": "arn:aws:iam::123456789000:role/hashicorp-aws-iam-role"}
-
+    backend_kwargs = {"connections_path": "airflow-connections", "variables_path": null, "mount_point": "airflow", "url": "http://127.0.0.1:8200", "auth_type": "aws_iam", "assume_role_kwargs": {"arn:aws:iam::123456789000:role/hashicorp-aws-iam-role", "RoleSessionName": "Airflow"}}
 
 Using multiple mount points
 """""""""""""""""""""""""""