librem5: update-dialog: Reduce the default width

This avoids the dialog being too wide by default.
2 jobs for librem5-3-36-1 in 0 seconds (queued for 74 minutes and 37 seconds)
Status Job ID Name Coverage
  Build
failed #293300
debian-stable-x86_64

failed #293299
fedora-x86_64

 
Name Stage Failure
failed
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failed
debian-stable-x86_64 Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
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