.*ws\d\d$ = used to filter out any source that ends with ws## .* wks\d\d$ = used to filter out any source that ends with wks## .*backup.* = used to filter out any source that has backup in the name
Save the changes and restart the probe.
It should be noted that if you had already discovered the vcenter previously, the sources will have made it into USM. You will need to find those sources in USM > Inventory and remove them from there, if they had already been discovered.