fix: maybe quotes around commit-range?

Author: dshemetov

.github/workflows/python-ci.yml

@@ -44,4 +44,4 @@ jobs:
       uses: akaihola/darker/.github/actions/[email protected]
     - name: Format (darker)
       run: |
-        DIFF="--diff" CHECK="--check" REVISION="--revision=${{ steps.commit-range.outputs.commit-range }}" make format
+        DIFF="--diff" CHECK="--check" REVISION="--revision='${{ steps.commit-range.outputs.commit-range }}'" make format