Add 3.7 back in the versions tested by CI

We want to keep testing 3.7 after all, because it was only marked EOL
recently, and that it still is pretty easy to do so (support in GH
actions).

Signed-off-by: Gus Monod <gmonod1@bloomberg.net>

.github/workflows/build.yml

@@ -90,10 +90,10 @@ jobs:
           (cd bloomberg-comdb2/build && sudo make install)
         '
       - uses: actions/checkout@v4
-      - name: 'Set up Python 3.8'
+      - name: 'Set up Python 3.7'
         uses: actions/setup-python@v4  # note that this step overwrites the PKG_CONFIG_PATH variable
         with:
-          python-version: '3.8'  # the lowest version that we support in CI
+          python-version: '3.7'  # the lowest version that we support in CI
       - name: Build sdist
         run: '
           sudo apt-get install -qy pkg-config &&
@@ -118,6 +118,7 @@ jobs:
           - '3.10'
           - '3.9'
           - '3.8'
+          - '3.7'
     steps:
       - name: Download comdb2 repo with build artifacts
         uses: actions/download-artifact@v3