Bump actions/upload-artifact from 5 to 6

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] <support@github.com>

Author: dependabot[bot]

.github/workflows/draft-pdf.yml

@@ -14,7 +14,7 @@ jobs:
           # This should be the path to the paper within your repo.
           paper-path: docs/paper/paper.md
       - name: Upload
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: paper
           # This is the output path where Pandoc will write the compiled

.github/workflows/publish.yml

@@ -16,7 +16,7 @@ jobs:
           python -m pip install --upgrade build
           python -m build
 
-      - uses: actions/upload-artifact@v5
+      - uses: actions/upload-artifact@v6
         with:
           path: dist/wsimod*