jfreereport_librepository: [deprecation] toURL() in File has been deprecated

http://docs.oracle.com/javase/6/docs/api/java/io/File.html#toURL()

Change-Id: I27d67f930ab15b69319a733b4bdedde834aba48d
Reviewed-on: https://gerrit.libreoffice.org/10530
Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>