Bump actions/upload-artifact from 4 to 7

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 4 to 7.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v4...v7)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/website.yml

@@ -133,7 +133,7 @@ jobs:
           done
         shell: bash
       - name: Store converted notebooks as artifacts
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v7
         with:
           name: converted-notebooks-${{ matrix.backend }}
           path: _converted
@@ -200,7 +200,7 @@ jobs:
         shell: bash
       - name: Deploy to GitHub artifacts
         if: github.repository == 'viskex/viskex.github.io' && github.ref != 'refs/heads/main'
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v7
         with:
           name: website
           path: |