GitHub Actions: Bump actions/upload-artifact from 5 to 6 (#45)

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-debug-apk.yml

@@ -44,14 +44,14 @@ jobs:
       run: bash .github/scripts/generate-lint-summary.sh
 
     - name: Upload debug APK
-      uses: actions/upload-artifact@v5
+      uses: actions/upload-artifact@v6
       with:
         name: org.fox.ttrss-debug-${{ github.run_number }}-${{ github.sha }}
         path: org.fox.ttrss/build/outputs/apk/debug/org.fox.ttrss-debug.apk
 
     - name: Upload full reports
       if: always()
-      uses: actions/upload-artifact@v5
+      uses: actions/upload-artifact@v6
       with:
         name: build-reports-${{ github.run_number }}
         path: |