feat(container): update image thanos to v12.21.0

| datasource | package                                   | from    | to      |
| ---------- | ----------------------------------------- | ------- | ------- |
| docker     | registry-1.docker.io/bitnamicharts/thanos | 12.20.1 | 12.21.0 |

cluster/apps/monitoring/thanos/helm-release.yaml

@@ -9,7 +9,7 @@ spec:
   chart:
     spec:
       chart: thanos
-      version: 12.20.1
+      version: 12.21.0
       sourceRef:
         kind: HelmRepository
         name: bitnami