delete a fortilink

I have a FortiGate 60E-POE running FortiOS 6.4 and 24port switch. I defined port internal8 as "dedicated for fortiswitch" in order to manage the 24port switch, and it's working fine.   Now I bought new 8port switch and want to connect it to the FortiGate with hardware switch as described in page 37 of the "FortiSwitch - Managed by FortiOS 6.2" manual (didn't fined it for OS 6.4) page 37 (https://fortinetweb.s3.am...ed_by_FortiOS_6.2.pdf) In order to do that, it looks like I need to delete the existing FortiLink on internal8, and I could not find a way to do that. any help would be appreciated :)