Fix check_unflagged_fraction crash when using toil (RAP-128)

The step check_unflagged_fraction is not properly running with toil. The aim of this MR is to fix this bug.

Ticket: RAP-128

steps/check_unflagged_fraction.cwl

@@ -50,6 +50,8 @@ requirements:
           cwl_output['unflagged_fraction']  = unflagged_fraction
           cwl_output['frequency']           = ref_freq
 
+          if 'listing' in inputs['msin'].keys():
+             del inputs['msin']['listing']
           if flagged != 'None':
              cwl_output['msout']            = [inputs['msin']]
              cwl_output['msout'][0]['path'] = output['filename']