Require multipart URLs even if limit is size

AWS will complain if no Content-Length is not specified, so we need to
use multipart URLs if no length is available.

lib/object_storage/direct_upload.rb

@@ -206,11 +206,7 @@ module ObjectStorage
     end
 
     def requires_multipart_upload?
-      config.aws? && !has_length && can_use_multipart_upload? && !use_workhorse_s3_client?
-    end
-
-    def can_use_multipart_upload?
-      (maximum_size == 0) || (maximum_size > MINIMUM_MULTIPART_SIZE)
+      config.aws? && !has_length && !use_workhorse_s3_client?
     end
 
     def upload_id

spec/lib/object_storage/direct_upload_spec.rb

@@ -359,8 +359,12 @@ RSpec.describe ObjectStorage::DirectUpload do
           context 'when maximum upload size is < 5 MB' do
             let(:maximum_size) { 1024 }
 
-            it 'does not include multipart URLs' do
-              expect(subject).not_to include(:MultipartUpload)
+            it 'returns only 1 part' do
+              expect(subject[:MultipartUpload][:PartURLs].length).to eq(1)
+            end
+
+            it 'part size is minimum, 5MB' do
+              expect(subject[:MultipartUpload][:PartSize]).to eq(5.megabyte)
             end
           end