try an env var instead

.github/workflows/main.yml

@@ -8,7 +8,7 @@ jobs:
       fail-fast: false
       matrix:
         # Tested versions based on dates in https://devguide.python.org/versions/#versions
-        python-version: ${{fromJson(secrets.PYTHON_VERSIONS_ACTIVE)}}
+        python-version: ${{fromJson(env.PYTHON_VERSIONS_ACTIVE)}}
     steps:
       - uses: actions/checkout@v2
       - name: Setup python