style(rubocop): Style/MultilineBlockChain

lib/postal/dkim_header.rb

@@ -34,14 +34,15 @@ module Postal
 
     def normalized_headers
       [].tap do |new_headers|
-        headers.select { |h|
+        dkim_headers = headers.select { |h|
           h.match(%r{
             ^(
               from|sender|reply-to|subject|date|message-id|to|cc|mime-version|content-type|content-transfer-encoding|
               resent-to|resent-cc|resent-from|resent-sender|resent-message-id|in-reply-to|references|list-id|list-help|
               list-owner|list-unsubscribe|list-subscribe|list-post
             ):}ix)
-        }.each do |h|
+        }
+        dkim_headers.each do |h|
           new_headers << normalize_header(h)
         end
       end