jurt: encode(String) in URLEncoder has been deprecated

Change-Id: I914985aa73653e0fb08200ddd06ad5b914087e3a
Reviewed-on: https://gerrit.libreoffice.org/11446
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>