[Savannah-hackers-public] renamingprojectgroup instructions

[Karl Berry]

https://savannah.gnu.org/maintenance/RenamingProjectGroup refers to the
file /subsystems/accounts/etc/group, which doesn't exist.  Is that
/subsystems/accounts/etc/group now?  But actually I think we should just
delete that text, since the next advice "Use the automated script, at
~/infra/maintenance/rename_project.sh" appears to be the right one :).

I don't have an urgent need to rename a group, just ran across this
page while thinking about it ...