Update actions/upload-artifact action to v6

Author: renovate[bot]

.github/workflows/build.yml

@@ -36,7 +36,7 @@ jobs:
         run: task test
 
       - name: Upload build artifacts
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: sqlite-mcp
           path: build/sqlite-mcp