screen-share: destroy seat on remove

Destroy seats when they get removed. This makes sure that seats
properly disappear when screen-share RDP clients disconnect.
There will be no excessive amount of mouse pointer anymore after
several client connection/disconnections.

Signed-off-by: Stefan Agner <stefan@agner.ch>
2 jobs for screen-share-destroy-seats in 59 seconds
Status Job ID Name Coverage
  Container Prep
passed #373433
container_prep

00:00:23

 
  Build
passed #373434
build-native-meson

00:00:36