Fix flaky time related spec

Also removes test from quarantine

spec/models/ci/pipeline_schedule_spec.rb

@@ -128,10 +128,12 @@ describe Ci::PipelineSchedule do
     context 'when pipeline schedule runs every minute' do
       let(:pipeline_schedule) { create(:ci_pipeline_schedule, :every_minute) }
 
-      it "updates next_run_at to the sidekiq worker's execution time", :quarantine do
+      it "updates next_run_at to the sidekiq worker's execution time" do
+        Timecop.freeze do
           expect(pipeline_schedule.next_run_at).to eq(cron_worker_next_run_at)
         end
       end
+    end
 
     context 'when there are two different pipeline schedules in different time zones' do
       let(:pipeline_schedule_1) { create(:ci_pipeline_schedule, :weekly, cron_timezone: 'Eastern Time (US & Canada)') }