[EKS] [request]: Anomaly with containerd 2.1.2

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Can find this error occuring with the pods stuck in "CreateContainerError" state for AMI release versions that have containerd version running at 2.2.1 where secrets are not encoded in base64 or in some other binary format:

````
Error: Error: grpc: error unmarshalling request: string field contains invalid UTF-8
````

Example secret file:

````
apiVersion: v1
kind: Secret
metadata:
name: utf8-error-secret
type: Opaque
data:
# This contains invalid UTF-8 when base64 decoded
config: a2V5PXZhbHVlgIH/
````
AMI details:

````
AMI: ami-0c8ded6af22dcae07
amazon-eks-node-al2023-x86_64-standard-1.32-v20260317
````

Corrected secret file:

````
apiVersion: v1
kind: Secret
metadata:
name: utf8-error-secret
type: Opaque
data:
config: YTJWNVBYWmhiSFZsZ0lILw==
````

Also could find that this was not occuring on AMIs that are not running containerd version 2.1.5.

Ask:

Please update this somewhere in the documentation or release notes to support users who upgrade AMI release version or change the AMI ID that upgrades the containerd version too.

Start by verifying the AMI and containerd version details given in the issue, including the differing 2.1.2, 2.2.1, and 2.1.5 references. Find the relevant EKS documentation or release-notes entry, then document the invalid UTF-8 secret behavior and affected AMI upgrades; done when users can identify and avoid the incompatibility.

Written by the indexing model from the issue text.