Hi @bigapplebo, 

You can use :

https://beta.steemconnect.com/sign/delegateVestingShares?delegator=bigapplebo&delegatee=minnowbooster&vesting_shares=0%20SP

or

go to https://steemworld.org/@bigapplebo , select delegations,click outgoing, click edit and zero your delegation to Minnowbooster, please note that it would require you to authenticate that request.

Regards,
@trev03