Use let! feedback:

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5347/diffs#note_13173336

let! is not very flexible but I guess it's fine since this is not in
top-level anyway.

spec/models/build_spec.rb

@@ -675,14 +675,10 @@ describe Ci::Build, models: true do
   end
 
   describe 'Project#latest_successful_builds_for' do
-    let(:build) do
+    let!(:build) do
       create(:ci_build, :artifacts, :success, pipeline: pipeline)
     end
 
-    before do
-      build
-    end
-
     context 'with succeed pipeline' do
       it 'returns builds from ref' do
         builds = project.latest_successful_builds_for('fix')