[admin] Remove Puppet 4 server VMs

data/grid5000/sites/grenoble/servers/puppet4.json

data/grid5000/sites/lille/servers/puppet4.json

data/grid5000/sites/luxembourg/servers/puppet4.json

data/grid5000/sites/lyon/servers/puppet4.json

data/grid5000/sites/nancy/servers/puppet4.json

data/grid5000/sites/nantes/servers/puppet4.json

data/grid5000/sites/rennes/servers/puppet4.json

data/grid5000/sites/sophia/servers/puppet4.json

input/grid5000/sites/grenoble/servers/virtual.yaml

input/grid5000/sites/lille/servers/virtual.yaml

input/grid5000/sites/luxembourg/servers/virtual.yaml

input/grid5000/sites/lyon/servers/virtual.yaml

input/grid5000/sites/nancy/servers/virtual.yaml

input/grid5000/sites/nantes/servers/virtual.yaml

input/grid5000/sites/rennes/servers/virtual.yaml

input/grid5000/sites/sophia/servers/virtual.yaml