bluez: Fix translatable strings spanning multiple lines

gettext versions older than 0.18.3 don’t support multi-line translatable
strings in Vala source code. Rather than bumping the gettext version,
don’t split the strings.

In future, the gettext dependency can be bumped to 0.18.3 and the
strings can be line-wrapped again.

https://bugzilla.gnome.org/show_bug.cgi?id=720707