Document the need for the permis-test user to be a member of >1 group
Document the need for the permis-test user to be a member of >1 group

Signed-off-by: Matthew Vernon <d2337109245c21c6e400ba5f0470cfb01956d9f2@sanger.ac.uk>

hpc/charliecloud,hpc/charliecloud,hpc/charliecloud