Fix grammar typo

Add missing "a"

Author: janakdr

site/en/tutorials/text/word2vec.ipynb

@@ -215,7 +215,7 @@
         "id": "Cl0rSfHjt6Mf"
       },
       "source": [
-        "A negative sample is defined as a (target_word, context_word) pair such that the context_word does not appear in the `window_size` neighborhood of the target_word. For the example sentence, these are few potential negative samples (when `window_size` is 2).\n",
+        "A negative sample is defined as a (target_word, context_word) pair such that the context_word does not appear in the `window_size` neighborhood of the target_word. For the example sentence, these are a few potential negative samples (when `window_size` is 2).\n",
         "\n",
         "```\n",
         "(hot, shimmered)\n",