Move Intel CI tests from ubuntu-latest to ubuntu-20.04 (#918)

co-author: Matthew Masarik

Author: JessicaMeixner-NOAA

.github/workflows/intel.yml

@@ -8,7 +8,7 @@ concurrency:
 
 # Set I_MPI_CC/F90 so Intel MPI wrapper uses icc/ifort instead of gcc/gfortran
 env:
-  cache_key: intel6
+  cache_key: intel7
   CC: icc
   FC: ifort
   CXX: icpc
@@ -21,7 +21,7 @@ env:
 
 jobs:
   setup:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04 
 
     steps:
 
@@ -91,7 +91,7 @@ jobs:
     strategy:
       matrix:
         switch: [Ifremer1, NCEP_st2, NCEP_st4, ite_pdlib, NCEP_st4sbs, NCEP_glwu, OASACM, UKMO, MULTI_ESMF]
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04 
 
     steps:
       - name: checkout-ww3