nixosTests.ft2-clone: make OCR more robust

nixos/tests/ft2-clone.nix

···
 
       machine.wait_for_window(r"Fasttracker")
       machine.sleep(5)
-      # One of the few words that actually get recognized
-      if "Songlen" not in machine.get_screen_text():
-          raise Exception("Program did not start successfully")
+      machine.wait_for_text(r"(Songlen|Repstart|Time|About|Nibbles|Help)")
       machine.screenshot("screen")
     '';
 })