Docker image needs to be renamed to align with other registries

The primary hivemind image used for haf_api_node should be renamed to registry.gitlab.syncad.com/hive/hivemind (currently it's named registry.gitlab.syncad.com/hive/hivemind/instance).

We want it to be easy for someone to switch between different docker registries. We have three options for users:

• docker hub, where the image is named hiveio/hivemind
• registry.hive.blog, where it's registry.hive.blog/hivemind
• registry.gitlab.syncad.com, where it needs to be named registry.gitlab.syncad.com/hive/hivemind

If we have consistent naming, someone can simply switch the HIVE_API_NODE_REGISTRY variable in their .env file and start pulling images from a different registry. We are shipping with the registry set to registry.hive.blog because it has better bandwidth than registry.gitlab.syncad.com, but people will need to switch their registry if they want to try out unpublished versions built by CI.