github: Update actions to fix deprecation errors

Author: slusarz

.github/workflows/documentation.yml

@@ -31,7 +31,7 @@ jobs:
           touch docs/.vitepress/dist/.nojekyll
       - name: Upload Artifact
         if: ${{ github.repository == 'dovecot/imaptest' && github.ref == 'refs/heads/main' }}
-        uses: actions/upload-pages-artifact@v2
+        uses: actions/upload-pages-artifact@v3
         with:
           path: docs/.vitepress/dist
 
@@ -46,4 +46,4 @@ jobs:
     steps:
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@v2
+        uses: actions/deploy-pages@v4