Possible incorrect granted permission in example RLS policy

[brandonw4]

For the RLS example policy "Allow authenticated group members with any role to read groups" Currently the permissive check is for all instead of for select.

https://github.com/point-source/supabase-tenant-rbac/blob/fda1410e22cb94b06004f610fe16d853cbeb640e/examples/policies/role_centric.sql#L43-L49