preferences-page-platforms-retro-row: Use HdyComboRow

Now that libhandy!594 is in
we can use it.
3 jobs for master in 20 minutes and 29 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #845216
flatpak
flatpak

00:17:09

passed #845215
flatpak
tests

00:06:22

 
  Deploy
passed #845217
nightly

00:03:19