sddm: Fix test.

For whatever reason, the OCR code is not detecting ALICE but is BOB.

OCR output from login screen (blank lines omitted):

> Session none + icewm
> 08:41 <
> Thursday, April 6, 2017
> BOB FOOBAR
> Select your user and enter password

nixos/tests/sddm.nix

@@ -24,7 +24,7 @@ let
         user = nodes.machine.config.users.extraUsers.alice;
       in ''
         startAll;
-        $machine->waitForText(qr/ALICE/);
+        $machine->waitForText(qr/BOB/);
         $machine->screenshot("sddm");
         $machine->sendChars("${user.password}\n");
         $machine->waitForFile("/home/alice/.Xauthority");