Upstream middle click paste defaults to false

see:
https://git.gnome.org/browse/gnome-settings-daemon/commit/?id=696e04d41a485f84870a98c85b819979928b69e9
https://git.gnome.org/browse/gnome-settings-daemon/tree/plugins/xsettings/gsd-xsettings-manager.c?#n347

https://bugzilla.gnome.org/show_bug.cgi?id=706603