I got in touch with the company and they gave me the instructions; it's crazy that Teams doesn't own the uninstall ability. To disconnect from Meekan's servers (and erase all your info) tell the robot "@meekan settings", to get to your settings page. It's in the last section: "Disconnect"
To remove to bot from your Teams, find the channel name, then click More options > Manage team. On the Apps tab, click Uninstall next to Meekan's name. Note that this will remove Meekan for your entire team, and not just for you.