Merge pull request aws#180 from matthieudelaro/master

Fix missing word

Author: djarpin

sagemaker-python-sdk/tensorflow_distributed_mnist/tensorflow_distributed_mnist.ipynb

@@ -120,7 +120,7 @@
     "When distributed training happens, the same neural network will be sent to the multiple training instances. Each instance will predict a batch of the dataset, calculate loss and minimize the optimizer. One entire loop of this process is called **training step**.\n",
     "\n",
     "### Syncronizing training steps\n",
-    "A [global step](https://www.tensorflow.org/api_docs/python/tf/train/global_step) is a global variable shared between the instances. It necessary for distributed training, so the optimizer will keep track of the number of **training steps** between runs: \n",
+    "A [global step](https://www.tensorflow.org/api_docs/python/tf/train/global_step) is a global variable shared between the instances. It's necessary for distributed training, so the optimizer will keep track of the number of **training steps** between runs: \n",
     "\n",
     "```python\n",
     "train_op = optimizer.minimize(loss, tf.train.get_or_create_global_step())\n",