Do you need to do this in the local GPO for some reason? (That’s what is viewed when you run gpedit.msc.) As has already been mentioned, setting this in a domain GPO would be the best approach.
It’s not an ideal solution, but if you must do this directly in the registry for some reason (instead of using Group Policy), this is the value associated with disabling that policy:
[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Reliability]
“ShutdownReasonOn”=dword:00000000