meson: adjust data/desktop.sh to avoid warning

```sh
$ ninja -C . totem-pot
ninja: Entering directory `.'
[0/1] Running external command totem-pot.
totem/data/org.gnome.Totem.desktop.in.in:19:0: warning: invalid non-blank line
```

Thanks Iñigo Martínez for the suggestion.
5 jobs from bye-intltool in 13 minutes and 25 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Test
passed #186042
build-fedora

00:10:16

passed #186039
flatpak

00:11:16

failed #186038
build-fedora

00:00:48

 
  Review
passed #186040
review

00:00:50

manual #186041
allowed to fail manual
stop_review