README: Update heading

Author: pH-7

README.md

@@ -9,7 +9,7 @@ _Simple script that parses data from open source food databases to the standard
 * 🎷 [Composer](https://getcomposer.org)
 
 
-## This can be slow... With big databases
+### Can be slow... with big databases
 
 When running `transform-csv-to-valid-file.php` with >= 2.4 GB CSV file for the food database provider, it can take nearly 5 days. Just keep your Web browser running and wait :)