Syntax:
UNINSTALL PLUGIN plugin_name

This statement removes an installed server plugin. It requires the
DELETE privilege for the mysql.plugin table.

plugin_name must be the name of some plugin that is listed in the
mysql.plugin table. The server executes the plugin's deinitialization
function and removes the row for the plugin from the mysql.plugin
table, so that subsequent server restarts will not load and initialize
the plugin. UNINSTALL PLUGIN does not remove the plugin's shared
library file.

URL: https://mariadb.com/kb/en/uninstall-plugin/

