Make the cases clear instead of having guards

This is easier to read for me, and feel free to disagree and close it.

/cc @ayufan

app/services/ci/process_pipeline_service.rb

@@ -31,13 +31,13 @@ module Ci
       current_status = status_for_prior_stages(index)
       created_builds_in_stage(index).select do |build|
-        process_build(build, current_status)
+        if HasStatus::COMPLETED_STATUSES.include?(current_status)
+          process_build(build, current_status)
+        end
       end
     end
     def process_build(build, current_status)
-      return false unless HasStatus::COMPLETED_STATUSES.include?(current_status)
-
       if valid_statuses_for_when(build.when).include?(current_status)
         build.enqueue
         true