chore(deps): update container image bitnami/alertmanager to 0.27.0@470dc1a by renovate (#25900)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [bitnami/alertmanager](https://redirect.github.com/bitnami/containers)
([source](https://redirect.github.com/bitnami/containers/tree/HEAD/bitnami/alertmanager))
| digest | `d24276b` -> `470dc1a` |

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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: 19.13.5
+version: 19.13.6

charts/premium/prometheus/values.yaml

@@ -6,7 +6,7 @@ thanosImage:
   tag: v0.36.1@sha256:e542959e1b36d5046083d1b64a7049c356b68a44a173c58b3ae7c0c9ada932d5
 alertmanagerImage:
   repository: bitnami/alertmanager
-  tag: 0.27.0@sha256:d24276be53bdcabe7667e683ed687ae413a7cd31986d4990b0986fb2f511c364
+  tag: 0.27.0@sha256:470dc1a7d476c0ac7383d29a0c31054d01228dc3b46bfea650e891b9a33695ec
 global:
   labels: {}
 workload: