Verify the challenge response but not PAM

as PAM should be enabled per default on the most distros:
 - dev-sec/chef-ssh-hardening#96
 - dev-sec/ansible-ssh-hardening#23
 - dev-sec/puppet-ssh-hardening#53

controls/sshd_spec.rb

@@ -276,10 +276,10 @@
 
 control 'sshd-26' do
   impact 1.0
-  title 'Server: Disable PAM'
-  desc 'Avoid challenge-response and password-based authentications.'
+  title 'Server: Disable challenge-response authentication'
+  desc 'Avoid challenge-response authentication.'
   describe sshd_config do
-    its('UsePAM') { should eq('no') }
+    its('ChallengeResponseAuthentication') { should eq('no') }
   end
 end