Update prep-chem version for GEFS

A new tag (gefs_v12.0.1-3) was created for the GEFSv12 para test
 On branch release/gefs_v12
	modified:   checkout.sh

sorc/checkout.sh

@@ -99,7 +99,7 @@ if [[ ! -d gsd_prep_chem.fd ]] ; then
     rc=$?
     ((err+=$rc))
     cd gsd_prep_chem.fd
-    git checkout gefs_v12.0.1-2
+    git checkout gefs_v12.0.1-3
     cd ${topdir}
 else
     echo 'Skip.  Directory gsd_prep_chem.fd already exists.'