correct URL for GeoGebraTube

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25387 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
4.9.129.0

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25388 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e