Update prompt-optimization-cookbook.ipynb to replace video with GIF and remove obsolete images

Author: rajpathak-openai

examples/gpt-5/prompt-optimization-cookbook.ipynb

@@ -15,12 +15,9 @@
    "source": [
     "The GPT-5 Family of models are the smartest models we’ve released to date, representing a step change in the models’ capabilities across the board. GPT-5 is particularly specialized in agentic task performance, coding, and steerability, making it a great fit for everyone from curious users to advanced researchers. \n",
     "\n",
-    "GPT-5 will benefit from all the traditional [prompting best practices](https://cookbook.openai.com/examples/gpt-5/gpt-5_prompting_guide), but to make optimizations and migrations easier, we are introducing the **[GPT-5  Prompt Optimizer](https://platform.openai.com/chat/edit?optimize=true) in our Playground to help users get started on **improving existing prompts** and **migrating prompts** for GPT-5 and other OpenAI models.**\n",
+    "GPT-5 will benefit from all the traditional [prompting best practices](https://cookbook.openai.com/examples/gpt-5/gpt-5_prompting_guide), but to make optimizations and migrations easier, we are introducing the **[GPT-5  Prompt Optimizer](https://platform.openai.com/chat/edit?optimize=true)** in our Playground to help users get started on **improving existing prompts** and **migrating prompts** for GPT-5 and other OpenAI models.\n",
     "\n",
-    "<video controls width=\"720\" preload=\"metadata\" autoplay loop muted playsinline>\n",
-    "  <source src=\"../../images/prompt-optimizer-3-22s.mp4\" type=\"video/mp4\">\n",
-    "  Your browser does not support the video tag.\n",
-    "</video>\n",
+    "![Prompt Optimizer demo](../../images/prompt-optimizer-3-22s.gif)\n",
     "\n",
     "In this cookbook we will show you how to use the Prompt Optimzer to get spun up quickly to solve your tasks with GPT-5, while demonstrating how prompt optimize can have measurable improvements. "
    ]