Cleanup let a bit, feedback:

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5347#note_13195683
and
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5347#note_13195692

another_artifacts was no longer used and then there's no point to
put let in outer scope anymore.

spec/requests/api/builds_spec.rb

@@ -213,17 +213,13 @@ describe API::API, api: true do
     end
 
     context 'find proper build' do
-      let(:another_artifacts) do
-        fixture_file_upload(Rails.root + 'spec/fixtures/dk.png', 'image/gif')
-      end
-
+      shared_examples 'a valid file' do
         let(:download_headers) do
           { 'Content-Transfer-Encoding' => 'binary',
             'Content-Disposition' =>
               "attachment; filename=#{build.artifacts_file.filename}" }
         end
 
-      shared_examples 'a valid file' do
         it { expect(response).to have_http_status(200) }
         it { expect(response.headers).to include(download_headers) }
       end