After updating to 7.5, I got an email which warned:
One or more legacy modules were found to be in use and were not attempted to be deleted: ip_manager, ip_monitor
I searched the forums but could find nothing for ip_manager or ip_monitor. So I did a general internet search and got this page which states:
URL: http://help.whmcs.com/m/75601/l/850628-troubleshooting-a-failed-to-remove-legacy-modules-error
Solution
The recommendation is to manually delete the module file