Revert Giac to older version

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@34784 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
4.9.281.0

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@34785 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e