Refactor the diff line to something more compact

lib/gitlab/checks/diff_check.rb

@@ -21,9 +21,7 @@ module Gitlab
         process_commits do |commit|
           validate_once(commit) do
             commit.raw_deltas.each do |diff|
-              [diff.new_path, diff.old_path].each do |path|
-                file_paths << path if path
-              end
+              file_paths.concat([diff.new_path, diff.old_path].compact)
 
               validate_diff(diff)
             end