Extend Events lifetime to 3 years instead of 2

We eventually want to avoid deleting any Events, see
https://gitlab.com/gitlab-org/gitlab/issues/24538.

app/workers/prune_old_events_worker.rb

@@ -6,13 +6,13 @@ class PruneOldEventsWorker
 
   # rubocop: disable CodeReuse/ActiveRecord
   def perform
-    # Contribution calendar shows maximum 12 months of events, we retain 2 years for data integrity.
+    # Contribution calendar shows maximum 12 months of events, we retain 3 years for data integrity.
     # Double nested query is used because MySQL doesn't allow DELETE subqueries on the same table.
     Event.unscoped.where(
       '(id IN (SELECT id FROM (?) ids_to_remove))',
       Event.unscoped.where(
         'created_at < ?',
-        (2.years + 1.day).ago)
+        (3.years + 1.day).ago)
       .select(:id)
       .limit(10_000))
     .delete_all

spec/workers/prune_old_events_worker_spec.rb

@@ -6,12 +6,12 @@ describe PruneOldEventsWorker do
   describe '#perform' do
     let(:user) { create(:user) }
 
-    let!(:expired_event) { create(:event, :closed, author: user, created_at: 25.months.ago) }
+    let!(:expired_event) { create(:event, :closed, author: user, created_at: 37.months.ago) }
     let!(:not_expired_1_day_event) { create(:event, :closed, author: user, created_at: 1.day.ago) }
     let!(:not_expired_13_month_event) { create(:event, :closed, author: user, created_at: 13.months.ago) }
-    let!(:not_expired_2_years_event) { create(:event, :closed, author: user, created_at: 2.years.ago) }
+    let!(:not_expired_3_years_event) { create(:event, :closed, author: user, created_at: 3.years.ago) }
 
-    it 'prunes events older than 2 years' do
+    it 'prunes events older than 3 years' do
       expect { subject.perform }.to change { Event.count }.by(-1)
       expect(Event.find_by(id: expired_event.id)).to be_nil
     end
@@ -26,9 +26,9 @@ describe PruneOldEventsWorker do
       expect(not_expired_13_month_event.reload).to be_present
     end
 
-    it 'leaves events from 2 years ago' do
+    it 'leaves events from 3 years ago' do
       subject.perform
-      expect(not_expired_2_years_event).to be_present
+      expect(not_expired_3_years_event).to be_present
     end
   end
 end