Update actions/upload-pages-artifact action to v3

Author: renovate[bot]

.github/workflows/pages.yml

@@ -40,7 +40,7 @@ jobs:
           source: ./docs
           destination: ./_site
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v2
+        uses: actions/upload-pages-artifact@56afc609e74202658d3ffba0e8f6dda462b719fa # v3
 
   # Deployment job
   deploy: