models2.json: use ChatML for Mistral OpenOrca (#1935)

Signed-off-by: Jared Van Bortel <jared@nomic.ai>

gpt4all-chat/metadata/models2.json

@@ -10,9 +10,10 @@
     "parameters": "7 billion",
     "quant": "q4_0",
     "type": "Mistral",
-    "systemPrompt": " ",
     "description": "<strong>Best overall fast chat model</strong><br><ul><li>Fast responses</li><li>Chat based model</li><li>Trained by Mistral AI<li>Finetuned on OpenOrca dataset curated via <a href=\"https://atlas.nomic.ai/\">Nomic Atlas</a><li>Licensed for commercial use</ul>",
-    "url": "https://gpt4all.io/models/gguf/mistral-7b-openorca.Q4_0.gguf"
+    "url": "https://gpt4all.io/models/gguf/mistral-7b-openorca.Q4_0.gguf",
+    "promptTemplate": "<|im_start|>user\n%1<|im_end|><|im_start|>assistant\n",
+    "systemPrompt": "<|im_start|>system\nYou are MistralOrca, a large language model trained by Alignment Lab AI. For multi-step problems, write out your reasoning for each step.\n<|im_end|>"
   },
   {
     "order": "b",