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/pypi.yml

@@ -36,7 +36,7 @@ jobs:
           python -m twine check dist/*
 
       - name: Upload sdist/ wheel
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: source-distribution
           path: dist

.github/workflows/test.yml

@@ -32,7 +32,7 @@ jobs:
 
       - name: Upload coverage
         if: inputs.os == 'ubuntu-latest' && inputs.python-version == '313'
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: code-coverage
           path: coverage.xml