build(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] <support@github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -138,7 +138,7 @@ jobs:
       shell: cmd
     - name: Upload artifact
       if: ${{ matrix.build_type == 'static' }}
-      uses: actions/upload-artifact@v5
+      uses: actions/upload-artifact@v6
       with:
         name: cmark windows ${{ matrix.build_type }}
         path: build/src/Debug/cmark.exe

.github/workflows/fuzz.yml

@@ -16,7 +16,7 @@ jobs:
         fuzz-seconds: 600
         dry-run: false
     - name: Upload Crash
-      uses: actions/upload-artifact@v5
+      uses: actions/upload-artifact@v6
       if: failure()
       with:
         name: artifacts