slack-desktop: update to 2.9.0
slack-desktop: update to 2.9.0

Closes #9448.

floGik/void-packages,necrophcodr/void-packages,EaterOfCode/void-packages,NeoChontrix/void-packages,coredumb/void-packages,floGik/void-packages,necrophcodr/void-packages,EaterOfCode/void-packages,necrophcodr/void-packages,NeoChontrix/void-packages,EaterOfCode/void-packages,necrophcodr/void-packages,EaterOfCode/void-packages,floGik/void-packages,NeoChontrix/void-packages,floGik/void-packages,NeoChontrix/void-packages,coredumb/void-packages,EaterOfCode/void-packages,coredumb/void-packages,coredumb/void-packages,floGik/void-packages,floGik/void-packages,coredumb/void-packages,NeoChontrix/void-packages,necrophcodr/void-packages,coredumb/void-packages,NeoChontrix/void-packages