Moved from "Convertors" to "Support"
("Convertors is for converting from other BB packages to phpBB, not just updating from an older phpBB installation.)
All you need to do is upload all the files from the full 2.0.22 install package, except for config.php (you must be careful to keep your existing config.php, make a backup copy of it now).
Then, browse to http://your_forum_address/install/update_to_latest.php
This will update your database to the latest specification.
Then delete the entire install directory and contrib directory. Do not run the install.php script at any time.