github CI test runner, third attempt

Signed-off-by: Tim Bray <tbray@textuality.com>

Author: timbray

.github/workflows/tests.yaml

@@ -56,7 +56,7 @@ jobs:
 
       - if: steps.codecov-enabled.outputs.files_exists == 'true'
         name: Upload Codecov Report
-        uses: codecov/codecov-action@latest
+        uses: codecov/codecov-action@v4
 
       - name: Verify git clean
         shell: bash