Update grafana/tempo:latest Docker digest to 21d5638 (#11)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| grafana/tempo | digest | `a4361e6` -> `21d5638` |

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### Configuration

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Reviewed-on: #11
Co-authored-by: Renovate Bot <renovate-bot@valverde.cloud>
Co-committed-by: Renovate Bot <renovate-bot@valverde.cloud>

compose.yml

@@ -48,7 +48,7 @@ services:
 
   tempo:
     <<: *service-base
-    image: grafana/tempo:latest@sha256:a4361e69d7f260f0a465f92b090dc53f5b07b81151b10c1ca92fad9948dc258f
+    image: grafana/tempo:latest@sha256:21d563828e55c2ee4e79f9a4bf9e1abfa4f585213f9f5e49d9b98e44fac92f2c
     command: [-config.file=/etc/tempo.yaml]
     volumes:
       - ./telemetry/tempo.yaml:/etc/tempo.yaml