update to v4 of the GH artifact action

Author: aerispaha

.github/workflows/documentation.yml

@@ -38,7 +38,7 @@ jobs:
         run: sphinx-build docs docs/build
 
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v2
+        uses: actions/upload-pages-artifact@v4
         with:
           # Upload build
           path: './docs/build'