Pin tokio-util to 0.7.11 to fix msrv build

Author: G8XSU

.github/workflows/build.yml

@@ -28,6 +28,7 @@ jobs:
             cargo update -p proptest --precise "1.2.0" --verbose # proptest 1.3.0 requires rustc 1.64.0
             cargo update -p regex --precise "1.9.6" --verbose # regex 1.10.0 requires rustc 1.65.0
             cargo update -p tokio --precise "1.38.1" --verbose # tokio v1.39.0 requires rustc 1.70 or newer
+            cargo update -p tokio-util --precise "0.7.11" --verbose # tokio-util v0.7.12 requires rustc 1.70 or newer
       - name: Build on Rust ${{ matrix.toolchain }}
         run: cargo build --verbose --color always
       - name: Check formatting