Fix interval in NormalizeLdapExternUids spec

The background migration interval has been reduced from 5 minutes to 2
minutes, so we have to adjust this migration accordingly.

spec/migrations/normalize_ldap_extern_uids_spec.rb

@@ -27,11 +27,11 @@ describe NormalizeLdapExternUids, :migration, :sidekiq do
         migrate!
 
         expect(BackgroundMigrationWorker.jobs[0]['args']).to eq([described_class::MIGRATION, [1, 2]])
-        expect(BackgroundMigrationWorker.jobs[0]['at']).to eq(5.minutes.from_now.to_f)
+        expect(BackgroundMigrationWorker.jobs[0]['at']).to eq(2.minutes.from_now.to_f)
         expect(BackgroundMigrationWorker.jobs[1]['args']).to eq([described_class::MIGRATION, [3, 4]])
-        expect(BackgroundMigrationWorker.jobs[1]['at']).to eq(10.minutes.from_now.to_f)
+        expect(BackgroundMigrationWorker.jobs[1]['at']).to eq(4.minutes.from_now.to_f)
         expect(BackgroundMigrationWorker.jobs[2]['args']).to eq([described_class::MIGRATION, [5, 5]])
-        expect(BackgroundMigrationWorker.jobs[2]['at']).to eq(15.minutes.from_now.to_f)
+        expect(BackgroundMigrationWorker.jobs[2]['at']).to eq(6.minutes.from_now.to_f)
         expect(BackgroundMigrationWorker.jobs.size).to eq 3
       end
     end