Disable the "GPUs" option when there is only one GPU.

In that case, 'Auto' seems to be the safe choice, and overriding it can break games. So we won't allow this.

Resolves #5304 again.

lutris/sysoptions.py

@@ -111,6 +111,7 @@ system_options = [  # pylint: disable=invalid-name
         "label": _("GPU"),
         "choices": get_gpu_list,
         "default": "",
+        "condition": lambda: len(GPUS) > 1,
         "help": _("GPU to use to run games"),
     },
     {