chore(helm): update image docker.io/bitnami/alertmanager 0.27.0 → 0.28.0 (#30956)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
|
[docker.io/bitnami/alertmanager](https://redirect.github.com/bitnami/containers)
([source](https://redirect.github.com/bitnami/containers/tree/HEAD/bitnami/alertmanager))
| minor | `0062fb9` -> `643bcef` |

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charts/premium/prometheus/values.yaml

@@ -6,7 +6,7 @@ thanosImage:
   tag: v0.37.2@sha256:4ec6df40fdb921de162677b321057caa8fb8324c65f4cfae9568ed55c4469e2c
 alertmanagerImage:
   repository: docker.io/bitnami/alertmanager
-  tag: 0.27.0@sha256:0062fb9fb12c88ea0f2be2fc9a2ab70019a983738238d9160bbf8db7d96bc4e9
+  tag: 0.28.0@sha256:643bcefdb4dc4745ac7077278d54a80ff374e621b7287cf84dbbe6b01e0208c9
 global:
   labels: {}
 workload: