x11-wm/cosmic-comp: update to 1.0.0.a.7

Changes: https://github.com/pop-os/cosmic-comp/compare/epoch-1.0.0-alpha.5.1...epoch-1.0.0-alpha.7
Reported by: Repology

(cherry picked from commit c49d6c91445992bbc03588ff1ca79f98ff7fc909)