tidy: Update comment

np.astype became available in numpy 2.1
The special case is still needed, however, to support older numpy as well as dask.

Author: danra

xarray/core/duck_array_ops.py

@@ -247,7 +247,7 @@ def astype(data, dtype, *, xp=None, **kwargs):
         xp = get_array_namespace(data)
 
     if xp == np:
-        # numpy currently doesn't have a astype:
+        # numpy<2.1 and dask don't have astype in their namespace
         return data.astype(dtype, **kwargs)
     return xp.astype(data, dtype, **kwargs)