Rename section local_nb_nodes.json to something more informative

[alyssadai]

Description

Some users have been confused on how to rename their deployed node (i.e., the name that appears in the Neurobagel graph dropdown), and our current docs section on this is not very easy to find. You have to look under the local_nb_nodes.json section under the "Configuring a node" page, but that assumes that you know that the relevant file is called local_nb_nodes.json.

Instead, we should rename this section to something like "Changing your node name" or similar.

Relevant documentation pages

https://neurobagel.org/config/#local_nb_nodesjson

Additional details

No response