Update doc/source/PreConfiguredSites.rst for gsi-addon-env on S4

doc/source/PreConfiguredSites.rst

@@ -558,13 +558,16 @@ For ``spack-stack-1.6.0`` with Intel, load the following modules after loading m
    module use /data/prod/jedi/spack-stack/spack-stack-1.6.0/envs/unified-env/install/modulefiles/Core
    module load stack-intel/2021.5.0
    module load stack-intel-oneapi-mpi/2021.5.0
-   module load stack-python/3.10.8
+   module load stack-python/3.10.13
    module unuse /opt/apps/modulefiles/Compiler/intel/non-default/22
    module unuse /opt/apps/modulefiles/Compiler/intel/22
    module available
 
 Note the two `module unuse` commands, that need to be run after the stack metamodules are loaded. Loading the Intel compiler meta module loads the Intel compiler module provided by the sysadmins, which adds those two directories to the module path. These contain duplicate libraries that are not compatible with our stack, such as ``hdf4``.
 
+.. note::
+   spack-stack-1.6.0 on S4 provides a chained environment `gsi-addon-env` for GSI with Intel. To use this environment, replace `unified-env` in the above `module use` statements with `gsi-addon-env`, and load module `stack-python/3.11.6` instead of `stack-python/3.10.13`.
+
 .. note::
 
    There is currently no support for GNU on S4, because recent updates to ``hdf5`` require a newer version of ``mpich`` (or other MPI library) than available on the system.