Cleanup depracated aws-irsa authType for Operator. Replaced by aws-iam #3327

Just for clarification: IRSA should remain supported!
Its just the naming of the config parameter.

s3.authType=aws-irsa has been changed to s3.authType=aws-iam as it supports both IRSA and EKS Pod Identity.

With v5 we supported both values, with only the new aws-iambeing documented.
With v6 the code references for aws-irsa (kept for backwards compatability with existing configs) should be removed.

Followup to #3314