WAFS tag update (gfs_wafs.v6.0.20) for v16 post-implementation fixes

Tag updates:

    1. Change WAFS 1.25 products (except for icing & turbulence) on model pressure levels.
    2. Add CAT and MWT back to 0.25 WAFS product

Refs: #1

sorc/checkout.sh

@@ -95,7 +95,7 @@ if [[ ! -d gfs_wafs.fd ]] ; then
     rm -f ${topdir}/checkout-gfs_wafs.log
     git clone --recursive https://github.com/NOAA-EMC/EMC_gfs_wafs.git gfs_wafs.fd >> ${topdir}/checkout-gfs_wafs.log 2>&1
     cd gfs_wafs.fd
-    git checkout gfs_wafs.v6.0.19
+    git checkout gfs_wafs.v6.0.20
     cd ${topdir}
 else
     echo 'Skip.  Directory gfs_wafs.fd already exists.'