Upgrade actions/upload-pages-artifact to version 3 in GH pages workflow

Author: mmenozzi

.github/workflows/jekyll-gh-pages.yml

@@ -47,7 +47,7 @@ jobs:
         env:
             JEKYLL_ENV: production
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v2
+        uses: actions/upload-pages-artifact@v3
         with:
             path: "docs/_site/"