chore(deps): update container image bitnami/alertmanager to 0.27.0@a15427d by renovate (#24833)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [bitnami/alertmanager](https://togithub.com/bitnami/containers)
([source](https://togithub.com/bitnami/containers/tree/HEAD/bitnami/alertmanager))
| digest | `5e0da79` -> `a15427d` |

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This PR has been generated by [Renovate
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charts/premium/prometheus/Chart.yaml

@@ -42,4 +42,4 @@ sources:
   - https://hub.docker.com/r/bitnami/prometheus
   - https://quay.io/thanos/thanos
 type: application
-version: 19.9.1
+version: 19.9.2

charts/premium/prometheus/values.yaml

@@ -6,7 +6,7 @@ thanosImage:
   tag: v0.36.0@sha256:785c18b9f06b1b23c9e0040a77b072a424bfe2f018972751ec1bf8d61376a507
 alertmanagerImage:
   repository: bitnami/alertmanager
-  tag: 0.27.0@sha256:5e0da793db94725c066665bd21d68339869535836fe4774ce33073fb1d86b181
+  tag: 0.27.0@sha256:a15427d94ec3a7458b7d98e1c1d20099bb4fd5e8d9ff75428417f9791c153186
 global:
   labels: {}
 workload: