Update upload-artifact to v4 due to github deprecation (#262)

Author: XolphinMartijn

.github/workflows/build-draft-docs.yml

@@ -25,7 +25,7 @@ jobs:
           docx: true
           lint: true
           draft: ${{ !(github.event_name == 'push' && github.repository == 'cabforum/smime' && github.ref == 'refs/heads/main') }}
-      - uses: actions/upload-artifact@v3
+      - uses: actions/upload-artifact@v4
         with:
           name: ${{ matrix.document }}-${{ github.event.pull_request.head.sha || github.sha }}
           path: |