Add clarifying text to Capacity Planning report
Add clarifying text to Capacity Planning report

The text explains that the disk space option is unsupported with
OpenStack providers
(transferred from ManageIQ/manageiq@9a897a3c4e1a1c012976deba273dbb5110adb8db)

ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic