correct datasetutil ref in code (replaced du by DatasetUtil)

Author: clemgoyens

hypernets_processor/surface_reflectance/surface_reflectance.py

@@ -47,7 +47,7 @@ def process_l1d(self, dataset_l1c):
                                                   dataset_l1d["wavelength"].values)
             dataset_l1d["epsilon"].values = epsilon
 
-            dataset_l1d["quality_flag"][dataset_l1d["scan"] == [i for i, x in enumerate(failSimil) if x]] = du.set_flag(
+            dataset_l1d["quality_flag"][dataset_l1d["scan"] == [i for i, x in enumerate(failSimil) if x]] = DatasetUtil.set_flag(
                 dataset_l1d["quality_flag"][dataset_l1d["scan"] == [i for i, x in enumerate(failSimil) if x]],
                 "simil_fail")