Minor docstring fix

Author: fchollet

keras/src/saving/saving_lib.py

@@ -511,9 +511,9 @@ def _load_model_from_fileobj(fileobj, custom_objects, compile, safe_mode):
 
 
 def save_weights_only(model, filepath, objects_to_skip=None):
-    """Save only the weights of a model to a target filepath (.weights.h5).
-
-    Note: only supports h5 for now.
+    """Save only the weights of a model to a target filepath.
+    
+    Supports both `.weights.h5` and `.keras`.
     """
     filepath = str(filepath)
     tmp_dir = None