Update hashicorp/vault Docker tag to v1.21.0 (#1832)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| hashicorp/vault | minor | `1.20.4` -> `1.21.0` |

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### Configuration

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Reviewed-on: #1832
Co-authored-by: Renovate Bot <renovate-bot@alexlebens.net>
Co-committed-by: Renovate Bot <renovate-bot@alexlebens.net>

clusters/cl01tl/platform/vault/values.yaml

@@ -12,7 +12,7 @@ vault:
     enabled: true
     image:
       repository: hashicorp/vault
-      tag: 1.20.4
+      tag: 1.21.0
     updateStrategyType: "RollingUpdate"
     logLevel: debug
     logFormat: standard
@@ -170,7 +170,7 @@ snapshot:
         snapshot:
           image:
             repository: hashicorp/vault
-            tag: 1.20.4
+            tag: 1.21.0
             pullPolicy: IfNotPresent
           command:
             - /bin/ash