feat(memory-store): Make cozo_data volume external (#616)

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> [!IMPORTANT]
> Set `cozo_data` volume to external in `docker-compose.yml`.
> 
>   - **Volumes**:
> - Set `cozo_data` volume to `external: true` in `docker-compose.yml`,
aligning with `cozo_backup`.
> 
> <sup>This description was created by </sup>[<img alt="Ellipsis"
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for 017823f. It will automatically
update as commits are pushed.</sup>

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memory-store/docker-compose.yml

@@ -33,5 +33,6 @@ services:
 
 volumes:
   cozo_data:
+    external: true
   cozo_backup:
     external: true