Fix typo

Author: hsm207

Diff for: Chapter1_Introduction/Ch1_Introduction_TFP.ipynb

@@ -1234,7 +1234,7 @@
         "\n",
         "    lambda_ = tf.gather(\n",
         "         [lambda_1, lambda_2],\n",
-        "         indices=tf.to_int32(tau * tf.cast(tf.size(count_data), tf.float32) <= tf.cast(tf.range(tf.size(count_data)))), tf.float32)\n",
+        "         indices=tf.to_int32(tau * tf.cast(tf.size(count_data), tf.float32) <= tf.cast(tf.range(tf.size(count_data)), tf.float32)))\n",
         "    rv_observation = tfd.Poisson(rate=lambda_)\n",
         " \n",
         "    return (\n",