[kubernetes] Fix coredns tag (#1469)

Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

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## What this PR does

fixes https://github.com/cozystack/cozystack/issues/1468

### Release note

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```release-note
[]
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## Summary by CodeRabbit

* **Chores**
* Pinned CoreDNS image to registry.k8s.io/coredns/coredns:v1.12.4 for
consistent, reproducible deployments.
  * Confirmed replica count remains at 2 (no scaling changes).

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/system/coredns/values.yaml

@@ -1,2 +1,5 @@
 coredns:
+  image:
+    repository: registry.k8s.io/coredns/coredns
+    tag: v1.12.4
   replicaCount: 2