[core][compiled graph] remove dead code (ray-project#48282)

If args is not a list, an exception will be thrown in the above if statement.

python/ray/dag/output_node.py

@@ -19,8 +19,6 @@ def __init__(
             args = list(args)
         if not isinstance(args, list):
             raise ValueError(f"Invalid input type for `args`, {type(args)}.")
-        if not isinstance(args, list):
-            args = (args,)
         super().__init__(
             args,
             {},