Update observability.md (#1514)

I tested this guide with the bookshop and I had to add the service
dependency in this format to mta.yaml:

```
    requires:
      - name: bookshop-cloud-logging
```

java/operating-applications/observability.md

@@ -394,7 +394,7 @@ Open Telemetry support using SAP BTP Cloud Logging Service leverages the [Open T
       - name: <srv-module>
         # ...
         requires:
-          - cloud-logging-instance
+          - name: cloud-logging-instance
     # ...
     resources:
       - name: cloud-logging-instance