docs: add missing newline to Stripe model-eval post

Author: joshbickett

examples/stripe_model_eval/selecting_a_model_for_stripe_conversion.ipynb

@@ -157,6 +157,7 @@
     "- **Segment by persona or use case:** Divide your audience (e.g., power users vs. newcomers, different industries) and see which models or prompts perform best for each group.\n",
     "- **Find the revenue–cost sweet spot:** Consider not only top-line revenue but also the cost to serve each model. The optimal choice may balance profit rather than maximize sales alone.\n",
     "- **Monitor long-term impact:** Look beyond immediate conversions. Track metrics like subscriber lifetime value, churn, or retention to optimize for sustainable growth.\n",
+    "\n",
     "There’s a lot of room to get creative with what you measure and how you experiment, so you can tune your product for what matters most to your team.\n",
     "For questions about this type of testing, feedback on your approach, or input on setting up your own test, feel free to reach out: [[email protected]](mailto:[email protected]).\n",
     "Here’s to building, experimenting, and letting your users—and your Stripe dashboard—guide the way.\n",