nlpsolver: fix javadoc error: bad use of '>'

Change-Id: Ibfaeef155982ce6eeefe8ef51eea9c2bddb12c46
Reviewed-on: https://gerrit.libreoffice.org/11244
Reviewed-by: Thomas Arnhold <thomas@arnhold.org>
Tested-by: Thomas Arnhold <thomas@arnhold.org>