Ensure autogenerated title does not cause failing spec

Hardcode the title into the object in the spec, so that an autogenerated
title (such as one starting with "O") does not cause the spec to fail.

changelogs/unreleased/hardcode-title-system-note.yml

+---
+title: Ensure autogenerated title does not cause failing spec
+merge_request: 8963
+author: brian m. carlson

spec/services/system_note_service_spec.rb

@@ -245,6 +245,8 @@ describe SystemNoteService, services: true do
   end
 
   describe '.change_title' do
+    let(:noteable) { create(:issue, project: project, title: 'Lorem ipsum') }
+
     subject { described_class.change_title(noteable, project, author, 'Old title') }
 
     context 'when noteable responds to `title`' do
@@ -252,7 +254,7 @@ describe SystemNoteService, services: true do
 
       it 'sets the note text' do
         expect(subject.note).
-          to eq "changed title from **{-Old title-}** to **{+#{noteable.title}+}**"
+          to eq "changed title from **{-Old title-}** to **{+Lorem ipsum+}**"
       end
     end
   end