Update GSI tag to gfsda.v16.1.3 (turn off IASI early) (#449)

- Emergency change occurred in operations during 2021092206 gdas cycle
to turn off the IASI from metop-a earlier than planned
- GSI global_satinfo.txt was updated to turn off IASI
- From SDM log on 20210921: 1ap. 1900Z - IDSB Chief Carissa requested
an ARFC for the SPA Team. The metopA "IASI" instrument is failing,
so they need to make a modification to dump jobs so models do not
assimilate the degraded data. They would like to make the change at
12Z tomorrow. NCO Deputy Director and SDM approved. (MBG)

Refs: #446

Externals.cfg

@@ -8,7 +8,7 @@ protocol = git
 required = True
 
 [GSI]
-tag = gfsda.v16.1.1a
+tag = gfsda.v16.1.3
 local_path = sorc/gsi.fd
 repo_url = https://github.com/NOAA-EMC/GSI.git
 protocol = git

sorc/checkout.sh

@@ -38,7 +38,7 @@ if [[ ! -d gsi.fd ]] ; then
     rm -f ${topdir}/checkout-gsi.log
     git clone --recursive https://github.com/NOAA-EMC/GSI.git gsi.fd >> ${topdir}/checkout-gsi.log 2>&1
     cd gsi.fd
-    git checkout gfsda.v16.1.1a
+    git checkout gfsda.v16.1.3
     git submodule update
     cd ${topdir}
 else