Add a note to the word2vec negative sampling outside the main diagram

Author: 8bitmp3

site/en/tutorials/text/word2vec.ipynb

@@ -615,6 +615,15 @@
         "![word2vec_negative_sampling](https://tensorflow.org/tutorials/text/images/word2vec_negative_sampling.png)"
       ]
     },
+    {
+      "cell_type": "markdown",
+      "metadata": {
+        "id": "37e53f07f67c"
+      },
+      "source": [
+        "Notice that words `temperature` and `code` are not part of the input sentence. They belong to the vocabulary like certain other indices used in the diagram above."
+      ]
+    },
     {
       "cell_type": "markdown",
       "metadata": {