Tweak spec and changelog title

changelogs/unreleased/241663-incident-sla-cron-job.yml

 ---
-title: Add Missed SLA label via Cron job
+title: Schedule adding "Missed SLA" label to issues
 merge_request: 44546
 author:
 type: added

ee/spec/models/issuable_sla_spec.rb

@@ -17,7 +17,7 @@ RSpec.describe IssuableSla do
 
       let_it_be(:project) { create(:project) }
       let_it_be_with_reload(:issue) { create(:issue, project: project) }
-      let_it_be_with_reload(:issuable_sla) { create(:issuable_sla, issue: issue, due_at: Time.current - 1.hour) }
+      let_it_be_with_reload(:issuable_sla) { create(:issuable_sla, issue: issue, due_at: 1.hour.ago) }
 
       context 'issue closed' do
         before do
@@ -30,14 +30,16 @@ RSpec.describe IssuableSla do
       context 'issue opened' do
         context 'due_at has not passed' do
           before do
-            issuable_sla.update!(due_at: Time.current + 1.hour)
+            issuable_sla.update!(due_at: 1.hour.from_now)
           end
 
           it { is_expected.to be_empty }
         end
 
+        context 'when due date has passed' do
           it { is_expected.to contain_exactly(issuable_sla) }
         end
       end
     end
+  end
 end