Bug#883487: mate-system-monitor: Don't recommend libgksu2-0

[Vlad Orlov]

Hi,

This can be safely dropped as libgksu isn't used by mate-system-monitor since 1.14.0.
It runs gksu binary instead [1]. Also since 1.18.0 it tries pkexec first before trying gksu [2].

(Support for both is optional, so no hard dependency is required.)

[1] https://github.com/mate-desktop/mate-system-monitor/commit/6e0ddb9837551bd33b2f0b75a8f83cb3d2d36927
[2] https://github.com/mate-desktop/mate-system-monitor/commit/ed81e790565663f1ddbdf0777efbd01b8b0e00ad