Update 01_How_TensorFlow_Works.ipynb

fixed syntax error

Author: Carlos Henrique Reis

01_Introduction/01_How_TensorFlow_Works/01_How_TensorFlow_Works.ipynb

@@ -66,7 +66,7 @@
     "\n",
     "    `a_var = tf.constant(42)`\n",
     "    `x_input = tf.placeholder(tf.float32, [None, input_size])`\n",
-    "    `y_input = tf.placeholder(tf.fload32, [None, num_classes])`\n",
+    "    `y_input = tf.placeholder(tf.float32, [None, num_classes])`\n",
     "\n",
     "5. Define the model structure.\n",
     "\n",