Github action: Update workflow to use upload-artifact v6

Author: joto

.github/workflows/clang-tidy.yml

@@ -53,7 +53,7 @@ jobs:
         shell: bash
         working-directory: build
       - name: Upload clang-tidy log
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         if: always()
         with:
           name: libosmium-${{ github.sha }}-clang-tidy-${{ matrix.clang }}-log