docs: Add EKS Pod Identity as supported (#4165)

Relates to #3899.

docs/sources/tempo/configuration/hosted-storage/s3.md

@@ -18,6 +18,7 @@ The following authentication methods are supported:
 - MinIO client credentials [configuration file](https://github.com/minio/mc/blob/master/docs/minio-client-configuration-files.md)
 - AWS IAM ([IRSA via WebIdentity](https://docs.aws.amazon.com/eks/latest/userguide/iam-roles-for-service-accounts.html),
 - AWS [EC2 instance role](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html))
+- AWS [EKS Pod Identity](https://docs.aws.amazon.com/eks/latest/userguide/pod-identities.html)
 
 The following IAM policy shows minimal permissions required by Tempo, where the bucket has already been created.