Update to use Rocky8 spack stack 1.6.0 on Jet (#22)

Jet has been upgraded to the Rocky8 Linux OS

Refs #21

modulefiles/fit2obs_jet.lua

@@ -2,7 +2,7 @@ help([[
 Build environment for fit2obs on Jet
 ]])
 
-prepend_path("MODULEPATH", "/mnt/lfs4/HFIP/hfv3gfs/role.epic/spack-stack/spack-stack-1.6.0/envs/unified-env/install/modulefiles/Core")
+prepend_path("MODULEPATH", "/mnt/lfs4/HFIP/hfv3gfs/role.epic/spack-stack/spack-stack-1.6.0/envs/gsi-addon-dev-rocky8/install/modulefiles/Core")
 
 local stack_intel_ver=os.getenv("stack_intel_ver") or "2021.5.0"
 local stack_impi_ver=os.getenv("stack_impi_ver") or "2021.5.1"