chore(deps): 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] <[email protected]>

Author: dependabot[bot]

.github/workflows/python.yml

@@ -79,7 +79,7 @@ jobs:
           FISH_API_KEY: ${{ secrets.FISH_API_KEY }}
 
       - name: Upload Test Artifacts
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         if: always()
         with:
           name: test-audio-output
@@ -98,7 +98,7 @@ jobs:
       - name: Check package
         run: uv run python -c "import fishaudio; print(f'fishaudio v{fishaudio.__version__}')"
       - name: Upload build artifacts
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: dist
           path: dist/