I've never used Orchestrator but if you really wanted to remove the extra CPU you could use the following PowerCLI script
Connect-VIServer <vscenter-server-name>
Stop-VM -VM <vmname> -Confirm:$false
Set-VM -VM <vmname> -NumCPU 1
Start-VM -VM <vmname> -Confirm:$false
Replace <vcenter-server-name> with the name of your vCenter Server or ESX Host
Replace <vmname> with the name of the VM you want to change
But as suggested you are probably best to just add the extra CPU to it and leave it like that, unless you only have 2 single core CPUs in your host or the CPUs are heavily used. A VM configured for 2 CPUs will have to wait for 2 CPU cores to be available before it can do any processing so on heavily loaded hosts adding a CPU can slow the VM down. However with todays multi-core CPUs this is less of an issue than it was years ago.