Removes legacy manage-groups from prod playbook
Removes legacy manage-groups from prod playbook

This role was removed in `fe8d2246e` and is no longer needed thanks to the
new dynamic inventory script. However, it was still referenced in the prod
playbook and this commit removes those references.

micahflee/securedrop,conorsch/securedrop,ehartsuyker/securedrop,ageis/securedrop,conorsch/securedrop,ageis/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,conorsch/securedrop,garrettr/securedrop,micahflee/securedrop,heartsucker/securedrop,garrettr/securedrop,ehartsuyker/securedrop,heartsucker/securedrop,garrettr/securedrop,conorsch/securedrop,conorsch/securedrop,heartsucker/securedrop,heartsucker/securedrop,micahflee/securedrop,ageis/securedrop,micahflee/securedrop,ehartsuyker/securedrop,garrettr/securedrop,ehartsuyker/securedrop,heartsucker/securedrop,ageis/securedrop