gio: Fix typo in g_file_info_set_attribute docs
gio: Fix typo in g_file_info_set_attribute docs

g_file_info_set_attribute mentions %G_ATTRIBUTE_TYPE_INVALID, but no
such value exists. It should be %G_FILE_ATTRIBUTE_TYPE_INVALID.

https://bugzilla.gnome.org/show_bug.cgi?id=796138

endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib