[scripts.train] Fix overlapping short options for datamodule and device

src/ptbench/scripts/train.py

@@ -125,7 +125,7 @@ logger = setup(__name__.split(".")[0], format="%(levelname)s: %(message)s")
 )
 @click.option(
     "--device",
-    "-d",
+    "-x",
     help='A string indicating the device to use (e.g. "cpu" or "cuda:0")',
     show_default=True,
     required=True,