TMSS-2618: used fine gridder

SAS/TMSS/backend/services/scheduling/lib/dynamic_scheduling.py

@@ -563,7 +563,7 @@ class Scheduler:
         # cancel and/or unschedule current units-in-the-way...
         # (only if possible, depending on priorities and other rules...)
         cancel_overlapping_running_observation_if_needed_and_possible(scheduling_unit, start_time)
-        unschededule_blocking_scheduled_units_if_needed_and_possible(scheduling_unit, start_time, self.search_gridder)
+        unschededule_blocking_scheduled_units_if_needed_and_possible(scheduling_unit, start_time, self.fine_gridder)
         unschededule_previously_scheduled_unit_if_needed_and_possible(scheduling_unit, start_time)
 
         # are there any blocking scheduled scheduling_units still in the way?