Update to upload-artifact v4 (#670)

fixes #669.

.github/workflows/ci.yaml

@@ -105,7 +105,7 @@ jobs:
           curl -L https://github.com/rust-lang-nursery/mdBook/releases/download/v${version}/mdbook-v${version}-x86_64-unknown-linux-gnu.tar.gz | tar xzf -
           echo `pwd` >> $GITHUB_PATH
       - run: (cd docs && mdbook build)
-      - uses: actions/upload-artifact@v1
+      - uses: actions/upload-artifact@v4
         with:
           name: doc-book
           path: docs/book
@@ -231,7 +231,6 @@ jobs:
           BUILD_REPOSITORY_ID: ${{ github.repository }}
           BUILD_SOURCEVERSION: ${{ github.sha }}
 
-
   test_success:
     runs-on: ubuntu-22.04
     needs: [typos, lint, test, self, publish-check, doc-book]