CI: update actions versions in docs workflow

Author: dnicolodi

.github/workflows/docs.yml

@@ -34,7 +34,7 @@ jobs:
           ref: ${{ github.event.push.tag || github.event.inputs.tag }}
       - run: python -m pip install .[docs]
       - run: python -m sphinx -W docs/ build/docs/
-      - uses: actions/upload-pages-artifact@v2
+      - uses: actions/upload-pages-artifact@v3
         with:
           path: build/docs/
 
@@ -48,4 +48,4 @@ jobs:
     runs-on: ubuntu-latest
     if: ${{ github.event.push.tag || github.event.inputs.tag }}
     steps:
-      - uses: actions/deploy-pages@v2
+      - uses: actions/deploy-pages@v4