1. Log into your Multicraft panel, and then access the FTP section. Alternatively, you can use a program like Filezilla or WinSCP to access your FTP server.
2. Open the "Commands.yml" file to edit it, it should look like this:
3. Underneath the "icanhasbukkit" value, insert the following:
list:
- []
It should look like this: 
4. Save, and close the file, and then restart your server.
Alternative:
As an Alternative, there are plugins that you can download to disable the /list displaying in the console, as well as other commands that it may be spamming, the following plugin is known to work for this:
Console Spam Fix