docs: Updated comments about `n_gpu_layers` in the Metal section (#16501)

Ref: https://github.com/langchain-ai/langchain/issues/16502

docs/docs/integrations/llms/llamacpp.ipynb

@@ -186,7 +186,7 @@
   },
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+   "execution_count": 1,
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@@ -223,7 +223,7 @@
   },
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+   "execution_count": 3,
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@@ -487,7 +487,7 @@
     "\n",
     "Two of the most important GPU parameters are:\n",
     "\n",
-    "- `n_gpu_layers` - determines how many layers of the model are offloaded to your Metal GPU, in the most case, set it to `1` is enough for Metal\n",
+    "- `n_gpu_layers` - determines how many layers of the model are offloaded to your Metal GPU.\n",
     "- `n_batch` - how many tokens are processed in parallel, default is 8, set to bigger number.\n",
     "- `f16_kv` - for some reason, Metal only support `True`, otherwise you will get error such as `Asserting on type 0\n",
     "GGML_ASSERT: .../ggml-metal.m:706: false && \"not implemented\"`\n",
@@ -501,7 +501,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "n_gpu_layers = 1  # Metal set to 1 is enough.\n",
+    "n_gpu_layers = 1  # Change this value based on your model and your GPU VRAM pool.\n",
     "n_batch = 512  # Should be between 1 and n_ctx, consider the amount of RAM of your Apple Silicon Chip.\n",
     "# Make sure the model path is correct for your system!\n",
     "llm = LlamaCpp(\n",
@@ -680,7 +680,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3.10.12 ('langchain_venv': venv)",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -694,7 +694,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.12"
+   "version": "3.11.6"
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