[gedit] 3.21 string changes: keyword and desktop actions

[Jeremy Bicha <jbicha ubuntu com>]

I pushed 2 commits that broke String Freeze. I'm sorry I wasn't able to
get these committed a week ago.

1) add some keywords from Ubuntu
2) correct the Desktop Actions (what you see when you right click an
app icon in the Activities Overview) for more consistency with other
GNOME apps

https://git.gnome.org/browse/gedit/commit/?id=d9fcb96
https://git.gnome.org/browse/gedit/commit/?id=bb69192

Thanks,
Jeremy Bicha