New comment by LinArcX on void-packages repository

https://github.com/void-linux/void-packages/pull/20538#issuecomment-611630080

Comment:
Due to [this issue](https://github.com/void-linux/void-packages/pull/20599#issuecomment-611489144), I've added `pantheon-agent-polkit` as runtime dependency of `pantheon-session`.