Fix invalid link for horovod cpu-only example (#600)

Author: lianghao208

examples/v2beta1/horovod/README.md

@@ -12,11 +12,11 @@ docker build -t horovod:latest .
 
 ## Create Mpijob
 
-The example mpijob is to run the horovod cpu-only example [tensorflow_mnist.py](https://raw.githubusercontent.com/horovod/horovod/master/examples/v2beta1/horovod/tensorflow_mnist.py).
+The example mpijob is to run the horovod cpu-only example [tensorflow_mnist.py](https://raw.githubusercontent.com/horovod/horovod/master/examples/tensorflow/tensorflow_mnist.py).
 
 ```bash
 kubectl create -f ./tensorflow-mnist.yaml
 ```
 ## v1 MPI job
 
-For old API kubeflow.org/v1 deploy manifest see [tensorflow_mnist.py](https://raw.githubusercontent.com/horovod/horovod/master/examples/v1/horovod/tensorflow-mnist-elastic.yaml)
+For old API kubeflow.org/v1 deploy manifest see [tensorflow-mnist-elastic.yaml](https://raw.githubusercontent.com/kubeflow/mpi-operator/v0.3.0/examples/horovod/tensorflow-mnist-elastic.yaml).