update GitHub Action: upload pages artifact

* v1 uses the deprecated version v3 of upload artifact

Signed-off-by: Armin Tänzer <armin.taenzer@tngtech.com>

Author: armintaenzertng

.github/workflows/docs.yml

@@ -28,7 +28,7 @@ jobs:
       - name: Generate docs
         run: pdoc spdx_tools -o docs/
       - name: Upload docs as artifact
-        uses: actions/upload-pages-artifact@v1
+        uses: actions/upload-pages-artifact@v3
         with:
           path: docs/