[Neuroimaging] Github team migration

[Matthew Brett]

Hi,

I've taken the liberty of applying the suggested migration of Github
teams from legacy model to current model:

https://help.github.com/en/articles/migrating-your-previous-admin-teams-to-the-improved-organization-permissions

I think this won't cause any important problem, but it does change the
default permission to create repositories in the Nipy organization,
for members of the project teams.  If you find you have lost that
permission, and you want it back - please email me, or the list, I'll
restore it.

Cheers,

Matthew