add back libcudnn9-headers-cuda-12

Author: jinyan-li1

pytorch/training/docker/2.8/py3/cu129/Dockerfile.gpu

@@ -105,6 +105,7 @@ RUN apt-get update \
     cuda-toolkit-12=${CUDA_VERSION}-1 \
     libcudnn9-cuda-12=${CUDNN_VERSION}-1 \
     libcudnn9-dev-cuda-12=${CUDNN_VERSION}-1 \
+    libcudnn9-headers-cuda-12=${CUDNN_VERSION}-1 \
     libhwloc-dev \
     libgomp1 \
     libibverbs-dev \