fix acceptance test with the new multidb role syntax

MongoDB only allows authentication to database where
the user has been created in, see
https://docs.mongodb.com/manual/core/security-users/#user-authentication-database

spec/acceptance/user_spec.rb

@@ -115,11 +115,5 @@ class { 'mongodb::server': }
         expect(r.stdout.chomp).to eq('1')
       end
     end
-
-    it 'allows the second user' do
-      shell("mongo testdb --quiet --eval 'db.auth(\"testuser2\",\"passw0rd\")'") do |r|
-        expect(r.stdout.chomp).to eq('1')
-      end
-    end
   end
 end