Fix ML intro notebook (#382)

* fix ml intro

* fix ml intro

tensorflow_v2/notebooks/0_Prerequisite/mnist_dataset_intro.ipynb

@@ -1,10 +1,8 @@
 {
  "cells": [
   {
-   "cell_type": "code",
-   "execution_count": null,
+   "cell_type": "markdown",
    "metadata": {},
-   "outputs": [],
    "source": [
     "\n",
     "# MNIST Dataset Introduction\n",
@@ -29,9 +27,7 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "metadata": {
-    "collapsed": true
-   },
+   "metadata": {},
    "outputs": [],
    "source": [
     "# Import MNIST\n",
@@ -55,9 +51,7 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "metadata": {
-    "collapsed": true
-   },
+   "metadata": {},
    "outputs": [],
    "source": [
     "# Get the next 64 images array and labels\n",
@@ -88,9 +82,9 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython2",
-   "version": "2.7.13"
+   "version": "2.7.18"
   }
  },
  "nbformat": 4,
- "nbformat_minor": 0
+ "nbformat_minor": 1
 }