Revert "FIXME: override datamodels.open"

This reverts commit 701a431.

liger_iris_pipeline/dark_current/dark_current_step.py

@@ -22,19 +22,6 @@ class DarkCurrentStep(Step):
 
     reference_file_types = ["dark"]
 
-    #FIXME - This will need to be ported to a new LigerIrisStep class
-    # I do not understand why this is necessary, in JWST it seems like
-    # this is not needed and works out of the box.
-    # Without this, the pipeline tries to call `datamodes.open` on a
-    # file that is already open, which gives the error:
-    # expected str, bytes or os.PathLike object, not LigerIrisDataModel
-    @classmethod
-    def _datamodels_open(cls, init, **kwargs):
-        if issubclass(init.__class__, stdatamodels.model_base.DataModel):
-            return init
-        else:
-            return datamodels.open(init, **kwargs)
-
     def process(self, input):
 
         # Open the input data model