Bump actions/upload-artifact from 3 to 4

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 3 to 4.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v3...v4)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/ci.yaml

@@ -240,7 +240,7 @@ jobs:
         run: python -m build
 
       - name: Upload distribution files
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: dist-packages
           path: dist/
@@ -304,7 +304,7 @@ jobs:
           mike set-default $MIKE_VERSION
 
       - name: Upload site
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: docs-site
           path: site/