Bump actions/upload-artifact from 5 to 6 (#75)

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 5 to 6.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v5...v6)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/build.yaml

@@ -133,7 +133,7 @@ jobs:
       - name: Build Documentation
         run: pixi run sphinx-build -M html . _build -W --keep-going -a -t draft
 
-      - uses: actions/upload-artifact@v5
+      - uses: actions/upload-artifact@v6
         with:
           name: beta-version
           path: _build/html
@@ -159,7 +159,7 @@ jobs:
         run: pixi run sphinx-build -M html . _build -W --keep-going -a
 
 
-      - uses: actions/upload-artifact@v5
+      - uses: actions/upload-artifact@v6
         with:
           name: tagged-version
           path: _build/html