x11/xdg-desktop-portal-wlr: track grim dependency for screenshots

$ flameshot gui
flameshot: error: Unable to capture screen
flameshot: error: Unable to capture screen
flameshot: info: Screenshot aborted.

https://github.com/emersion/xdg-desktop-portal-wlr/commit/2b659c42a7f6
(cherry picked from commit 01c668a293338955e8f4eb9b188748ecf504eca8)