doc: Fix documentation about n-gram overlap (#11549)

Fix the documentation in
https://python.langchain.com/docs/modules/model_io/prompts/example_selectors/ngram_overlap.
It's currently declaring unrelated variables, for example, `examples`
local variable is declared twice and the first one is overwritten
immediately.
  - **Issue:** N/A
  - **Dependencies:** N/A
- **Tag maintainer:** for a quicker response, tag the relevant
maintainer (see below),
  - **Twitter handle:** @dosuken123

docs/docs/modules/model_io/prompts/example_selectors/ngram_overlap.ipynb

@@ -19,32 +19,14 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "from langchain.prompts import PromptTemplate\n",
+    "from langchain.prompts import PromptTemplate, FewShotPromptTemplate\n",
     "from langchain.prompts.example_selector.ngram_overlap import NGramOverlapExampleSelector\n",
-    "from langchain.prompts import FewShotPromptTemplate, PromptTemplate\n",
     "\n",
     "example_prompt = PromptTemplate(\n",
     "    input_variables=[\"input\", \"output\"],\n",
     "    template=\"Input: {input}\\nOutput: {output}\",\n",
     ")\n",
     "\n",
-    "# Examples of a pretend task of creating antonyms.\n",
-    "examples = [\n",
-    "    {\"input\": \"happy\", \"output\": \"sad\"},\n",
-    "    {\"input\": \"tall\", \"output\": \"short\"},\n",
-    "    {\"input\": \"energetic\", \"output\": \"lethargic\"},\n",
-    "    {\"input\": \"sunny\", \"output\": \"gloomy\"},\n",
-    "    {\"input\": \"windy\", \"output\": \"calm\"},\n",
-    "]"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 2,
-   "id": "4f318f4b",
-   "metadata": {},
-   "outputs": [],
-   "source": [
     "# Examples of a fictional translation task.\n",
     "examples = [\n",
     "    {\"input\": \"See Spot run.\", \"output\": \"Ver correr a Spot.\"},\n",
@@ -60,10 +42,6 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "example_prompt = PromptTemplate(\n",
-    "    input_variables=[\"input\", \"output\"],\n",
-    "    template=\"Input: {input}\\nOutput: {output}\",\n",
-    ")\n",
     "example_selector = NGramOverlapExampleSelector(\n",
     "    # The examples it has available to choose from.\n",
     "    examples=examples,\n",