Fix for an untranslatable string in Documents

[Cosimo Cecchi <cosimoc gnome org>]

Hi all,

In bug 683973 [1] it has been reported that a string in Documents
causes problems for translation in certain languages such as Japanese.
Attached to the bug there's a patch which already had an 1/2 approval
for i18n by Andre on IRC.
Can I get a second approval and push it to git?

[1] https://bugzilla.gnome.org/show_bug.cgi?id=683973

Thanks,
Cosimo