Change python 3.8 to 3.9 in srt testing

3.9 is now the minimum supported by CIME

Author: billsacks

.github/workflows/srt.yml

@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [ 3.8, 3.11, 3.x ]
+        python-version: [ 3.9, 3.11, 3.x ]
     env:
       CC: mpicc
       FC: mpifort