make --speculative-draft-model an alias of --speculative-draft-model-path (#10246)

python/sglang/srt/server_args.py

@@ -1531,6 +1531,7 @@ class ServerArgs:
         )
         parser.add_argument(
             "--speculative-draft-model-path",
+            "--speculative-draft-model",
             type=str,
             help="The path of the draft model weights. This can be a local folder or a Hugging Face repo ID.",
         )