Preferences popover instructions for Munki cert hides last line

[Dave Lebbing]

v1.8 build 18057

On preferences dialog, the section for Munki has a popover with instructions that cuts off the last line. The user can scroll to see this but it could be good to just make the popover slightly longer so everything is shown at once.

[timothy perfitt]

This was moved to preferences and I could not find any issues with the popover.