Ignore system notes when indexing notes on work items

Before collecting the notes and internal notes for elasticsearch
indexing, downselect to the "user" scope to eliminate the usage of
all of the items that are marked as system notes.

EE: true
Changelog: fixed

ee/lib/search/elastic/references/work_item.rb

@@ -69,7 +69,7 @@ def model_klass
         private
 
         def populate_notes(target, data)
-          notes_internal, notes = target.notes.partition(&:internal)
+          notes_internal, notes = target.notes.user.partition(&:internal)
 
           internal_notes = notes_internal.sort_by(&:created_at).reverse.map(&:note).join("\n").presence
           data['notes_internal'] = internal_notes.truncate_bytes(NOTES_MAXIMUM_BYTES) if internal_notes

ee/spec/lib/search/elastic/references/work_item_spec.rb

@@ -95,7 +95,6 @@
       let_it_be(:note1) { create(:note_on_issue, noteable: project_work_item, project: project, note: 'Some pig') }
       let_it_be(:note2) { create(:note_on_issue, noteable: project_work_item, project: project, note: 'Terrific') }
       let_it_be(:note3) { create(:note, :internal, noteable: project_work_item, project: project, note: "Radiant") }
-
       let(:expected_hash) do
         base_work_item_hash.merge(
           root_namespace_id: project_work_item.namespace.root_ancestor.id,
@@ -121,6 +120,12 @@
         expect(indexed_json[:notes_internal]).to eq("Newest\n…")
       end
 
+      it 'does not include system notes' do
+        create(:note, :system, noteable: project_work_item, project: project, note: "Enchanting!")
+
+        expect(indexed_json[:notes]).not_to include('Enchanting!')
+      end
+
       context 'when add_work_item_type_correct_id migration is not complete' do
         before do
           set_elasticsearch_migration_to :add_work_item_type_correct_id, including: false