Doesn't Horovod support TensorFlow >= 2.16.1 ?

**Environment:**
1. Framework version: TensorFlow 2.16.1
2. Horovod version: 0.28.1
3. MPI version: 4.1.2
4. CUDA version: 12.3
5. NCCL version: 2.17.1
6. Python version: 3.10


**Bug report:**
    AttributeError: 'Variable' object has no attribute 'ref'

