chore(helm): update image public.ecr.aws/bitnami/alertmanager digest to 940e1ee (#32565)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
|
[public.ecr.aws/bitnami/alertmanager](https://redirect.github.com/bitnami/containers)
([source](https://redirect.github.com/bitnami/containers/tree/HEAD/bitnami/alertmanager))
| digest | `f46ec48` -> `940e1ee` |

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charts/premium/prometheus/Chart.yaml

@@ -42,4 +42,4 @@ sources:
   - https://github.com/truecharts/charts/tree/master/charts/premium/prometheus
   - https://quay.io/thanos/thanos
 type: application
-version: 22.2.0
+version: 22.2.1

charts/premium/prometheus/values.yaml

@@ -6,7 +6,7 @@ thanosImage:
   tag: v0.37.2@sha256:4ec6df40fdb921de162677b321057caa8fb8324c65f4cfae9568ed55c4469e2c
 alertmanagerImage:
   repository: public.ecr.aws/bitnami/alertmanager
-  tag: 0.28.0@sha256:f46ec48a7252702355d6b297db9aea26f14f1115aa4e0be978be26d9bac7bacb
+  tag: 0.28.0@sha256:940e1ee2d19339db9b11614b6508d42a9fb9ce1febb53a0d8cc07e4bf733eaa3
 global:
   labels: {}
 workload: