Remove feature flag to disable waiting on jobs

This has been running on GitLab.com with no ill effects for a few days.
If we did see problems, we'd expect to see them quickly.

app/workers/concerns/waitable_worker.rb

@@ -14,9 +14,7 @@ module WaitableWorker
       # are not likely to finish within the timeout. This assumes we can process
       # 10 jobs per second:
       # https://gitlab.com/gitlab-com/gl-infra/scalability/-/issues/205
-      if ::Feature.enabled?(:skip_job_waiter_for_large_batches)
       return bulk_perform_async(args_list) if args_list.length >= 10 * timeout
-      end
 
       waiter = Gitlab::JobWaiter.new(args_list.size, worker_label: self.to_s)
 

spec/workers/concerns/waitable_worker_spec.rb

@@ -58,21 +58,6 @@ describe WaitableWorker do
 
       worker.bulk_perform_and_wait(arguments, timeout: 2)
     end
-
-    context 'when the skip_job_waiter_for_large_batches flag is disabled' do
-      before do
-        stub_feature_flags(skip_job_waiter_for_large_batches: false)
-      end
-
-      it 'runs jobs over 10 * the timeout using a waiter key' do
-        arguments = 1.upto(21).map { |i| [i] }
-        arguments_with_waiter = arguments.map { |arg| arg + [anything] }
-
-        expect(worker).to receive(:bulk_perform_async).with(arguments_with_waiter)
-
-        worker.bulk_perform_and_wait(arguments, timeout: 2)
-      end
-    end
   end
 
   describe '.bulk_perform_inline' do