AvatarSelector: fix hidpi, avatars are to small

Fix https://source.puri.sm/Librem5/gnome-contacts/issues/37
2 jobs for pureos/sloppy in 4 minutes and 35 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Build Flatpak
failed #273391
flatpak
flatpak:master

00:04:35

 
  Build Arm Flatpak
skipped #273392
ARM64
flatpak-arm64:master
 
Name Stage Failure
failed
flatpak:master Build Flatpak
Uploading artifacts for failed job
Uploading artifacts...
WARNING: contacts-dev.flatpak: no matching files
WARNING: _build/meson-logs/: no matching files
ERROR: No files to upload
Uploading artifacts...
WARNING: _build/flatpak:master-report.xml: no matching files
ERROR: No files to upload
ERROR: Job failed: exit code 1