[CI]: ghcr.io/containerd/stargz-snapshotter:0.15.1-kind needs an arm64 variant

### Description

As such, it will fail on arm platforms with no emulation, in turn failing corresponding tests.

### Steps to reproduce the issue

_No response_

### Describe the results you received and expected

na

### What version of nerdctl are you using?

main

### Are you using a variant of nerdctl? (e.g., Rancher Desktop)

None

### Host information

_No response_