window: Reduce the hardcoded minimum size

This reduces the hardcoded minimum size to ensure it can fit phone
screens, moving the size request to the window's child to avoid having
to take shadows into account.
2 jobs for librem5-3-33-2 in 0 seconds (queued for 69 minutes)
latest
Status Job ID Name Coverage
  Build
failed #157215
build

failed #157216
build-flatpak

 
Name Stage Failure
failed
build-flatpak Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job log
failed
build Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job log