update workflow, use python 3.8 as oldest version

Author: Courtney Peverley

.github/workflows/fleximod_test.yaml

@@ -1,22 +1,18 @@
 on:
   pull_request:
-    branches: [ development ]
 jobs:
   fleximod-test:
     runs-on: ubuntu-latest
     strategy:
       matrix:
         # oldest supported and latest supported
-        python-version: ["3.7", "3.x"]
+        python-version: ["3.8", "3.x"]
     steps:
       - id: checkout-CESM
         uses: actions/checkout@v4
       - id: run-fleximod
         run: |
           $GITHUB_WORKSPACE/bin/git-fleximod update
           $GITHUB_WORKSPACE/bin/git-fleximod test
-#      - name: Setup tmate session
-#        if: ${{ failure() }}
-#        uses: mxschmitt/action-tmate@v3