auth: Fix ssh_auth_list() documentation.
auth: Fix ssh_auth_list() documentation.

The server will not return SSH_AUTH_METHOD_NONE.
(cherry picked from commit 9c376dd913b40bbcf9e0fc528f53e02c104b6c58)

mwgoldsmith/ssh,mwgoldsmith/ssh,mwgoldsmith/libssh,mwgoldsmith/ssh,mwgoldsmith/libssh,mwgoldsmith/ssh,mwgoldsmith/libssh,mwgoldsmith/libssh