Clarify version detection error message

This was supposed to imply that we couldn't configure the exploit for a
targetable version. Instead, it just read weirdly. I think it was
missing "to target" at the end. "Determine" is a much better word,
though, since we may be doing detection instead of mere configuration.

modules/exploits/unix/webapp/drupal_drupalgeddon2.rb

@@ -135,7 +135,7 @@ class MetasploitModule < Msf::Exploit::Remote
       print_status("Drupal #{@version} targeted at #{full_uri}")
       checkcode = CheckCode::Detected
     else
-      print_error('Could not configure Drupal version')
+      print_error('Could not determine Drupal version to target')
       return CheckCode::Unknown
     end