Fix the tokio-util version

from 0.7.12 supports 1.70.0 and later

.github/workflows/cont_integration.yml

@@ -39,6 +39,7 @@ jobs:
           cargo update -p proptest --precise "1.2.0"
           cargo update -p url --precise "2.5.0"
           cargo update -p tokio --precise "1.38.0"
+          cargo update -p tokio-util --precise "0.7.11"
       - name: Build
         working-directory: ./crates/chain
         run: cargo build -p "tdk_*" ${{ matrix.features }}