UX: Lower digest suppress period from a year to 6 months (#15023)

config/site_settings.yml

@@ -1068,7 +1068,7 @@ email:
     min: 0
     max: 20
   suppress_digest_email_after_days:
-    default: 365
+    default: 180
     max: 36500
   digest_suppress_categories:
     type: category_list

spec/jobs/enqueue_digest_emails_spec.rb

@@ -91,7 +91,7 @@ describe Jobs::EnqueueDigestEmails do
     end
 
     context 'regular users' do
-      let!(:user) { Fabricate(:active_user, last_seen_at: 360.days.ago) }
+      let!(:user) { Fabricate(:active_user, last_seen_at: (SiteSetting.suppress_digest_email_after_days - 1).days.ago) }
 
       it "returns the user" do
         expect(Jobs::EnqueueDigestEmails.new.target_user_ids).to eq([user.id])