scripting: encode(String) in URLEncoder has been deprecated

http://docs.oracle.com/javase/1.5.0/docs/api/java/net/URLEncoder.html

Change-Id: I9d9b40ecf0d76618376975c52e5d9f27ec4bae8e
Reviewed-on: https://gerrit.libreoffice.org/11438
Reviewed-by: Thomas Arnhold <thomas@arnhold.org>
Tested-by: Thomas Arnhold <thomas@arnhold.org>