Move "displayedVideos" to a computed property
Move "displayedVideos" to a computed property

Besides being cleaner this will make possible to fix the grid jumping
back to the first page when the  number of videos change.

Signed-off-by: Daniel Calviño Sánchez <bd7629e975cc0e00ea7cda4ab6a120f2ee42ac1b@gmail.com>

nextcloud/spreed,nextcloud/spreed,nextcloud/spreed