refactor: use a variable for the latest python version

Author: zimeg

.github/workflows/ci-build.yml

@@ -55,7 +55,7 @@ jobs:
           PYTHONPATH=$PWD:$PYTHONPATH pytest tests/slack_sdk/oauth/installation_store/test_sqlalchemy.py
           PYTHONPATH=$PWD:$PYTHONPATH pytest tests/slack_sdk/oauth/state_store/test_sqlalchemy.py
       - name: Confirm expected autogenerated reference exists
-        if: ${{ matrix.python-version == env.LATEST_PYTHON_VERSION }}
+        if: startsWith(matrix.python-version, env.LATEST_PYTHON_VERSION)
         run: |
           python -m venv .venv
           source .venv/bin/activate
@@ -71,7 +71,7 @@ jobs:
           token: ${{ secrets.CODECOV_TOKEN }}
           verbose: true
       - name: Upload test coverage to Codecov (only with latest supported version)
-        if: startsWith(matrix.python-version, '3.13')
+        if: startsWith(matrix.python-version, env.LATEST_PYTHON_VERSION)
         uses: codecov/codecov-action@5a1091511ad55cbe89839c7260b706298ca349f7 # v5.5.1
         with:
           token: ${{ secrets.CODECOV_TOKEN }}