Remove unused method in PatientStatusUpdater

This method implementation and an invocation from
`PatientStatusUpdater#update_programme_statuses!` was originally added in
this commit [1] in #6468.

Both the implementation and invocation were removed in this commit [2] in #6611.

Then the implementation was then re-added without the corresponding invocation
in this commit [3] within #6677 which was the "Version 8.1.0" pull request.

Since the method is never invoked, it's safe to remove it.

[1]: 25e876a
[2]: 29460d4
[3]: c66b757

Author: floehopper

app/lib/patient_status_updater.rb

@@ -160,23 +160,4 @@ def programme_types_per_session_id_and_year_group
           hash[session_id][year_group] << programme_type
         end
   end
-
-  # We preload this association separately because including it in the nested
-  # `patient_locations` preload (see includes above) caused the updater process
-  # to be killed, even with very small batches. The likely cause is memory pressure
-  # from eager loading a deeply nested association graph.
-  #
-  # Preloading it here for the distinct `Location` records in each batch keeps
-  # `StatusGenerator::Programme` query-free without incurring the cost of the
-  # larger nested preload.
-  def preload_location_programme_year_groups(batch)
-    locations = batch.flat_map(&:patient_locations).map(&:location).uniq
-
-    ActiveRecord::Associations::Preloader.new(
-      records: locations,
-      associations: {
-        location_programme_year_groups: :location_year_group
-      }
-    ).call
-  end
 end