[instructions] Replace ROS_PACKAGE_PATH by AMENT_PREFIX_PATH.

Author: florent-lamiraux

Diff for: doc/config/ubuntu-24.04.sh

@@ -8,7 +8,7 @@ export PYTHONPATH=$INSTALL_HPP_DIR/lib/python3.12/site-packages:$ROBOTPKG/lib/py
 
 export LD_LIBRARY_PATH=$INSTALL_HPP_DIR/lib:$ROBOTPKG/lib:$INSTALL_HPP_DIR/lib64:$LD_LIBRARY_PATH
 
-export ROS_PACKAGE_PATH=$INSTALL_HPP_DIR/share:$ROBOTPKG/share
+export AMENT_PREFIX_PATH=$INSTALL_HPP_DIR:$ROBOTPKG
 export CMAKE_PREFIX_PATH=$INSTALL_HPP_DIR:$ROBOTPKG:/usr
 
 if [ -f "${INSTALL_HPP_DIR}/etc/hpp-tools/bashrc" ]; then