fix: use correct setup-node action version v4

- actions/setup-node@v5 doesn't exist
- Latest version is v4

Author: alex-feel

.github/workflows/lint.yml

@@ -27,7 +27,7 @@ jobs:
         run: pip install pre-commit
 
       - name: Set up Node.js for markdownlint
-        uses: actions/setup-node@v5
+        uses: actions/setup-node@v4
         with:
           node-version: '20'