appdata: Put my email address as update_contact

Our mailing archives are slowly being replaced with discourse, and
seahorse-list was barely active anyway. At least this gives people
looking for a reply a bit more chance to actually receive one.
1 job for master in 22 minutes and 46 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build Flatpak
passed #300660
flatpak:master

00:22:46