how to disable a custom plugin that removes the admin bar

Newbie problem: I put up a site and didn’t want anyone to see the admin bar. I read about how to make a custom plugin to do that, and thought I would give it a try. It is now a “be careful what you wish for” problem. Nobody can get the admin bar, INCLUDING ME. I need to make some changes to the site, but can’t until I can either disable the plugin, or get at the admin bar some other way. Here’s the plugin:

<?php
/*
Plugin Name: Site Plugin for seed
Description: Site specific code changes seed
*/
/* Start Adding Functions Below this Line */

show_admin_bar(false); 

/* Stop Adding Functions Below this Line */
?>