Update grafana/tempo Docker tag to v2.8.0 (#1419)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| grafana/tempo | minor | `2.7.2` -> `2.8.0` |

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examples/example-exemplars-tail-sampling/docker-compose.yaml

@@ -52,7 +52,7 @@ services:
       - --enable-feature=native-histograms
       - --config.file=/prometheus.yaml
   tempo:
-    image: grafana/tempo:2.7.2
+    image: grafana/tempo:2.8.0
     network_mode: host
     volumes:
       - ./config/tempo-config.yaml:/config.yaml