Modify CHAT_SYSTEM_PROMPT, use $ and $$ style LaTeX delimiters only

packages/jupyter-ai-magics/jupyter_ai_magics/providers.py

@@ -54,7 +54,7 @@
 You are talkative and you provide lots of specific details from the foundation model's context.
 You may use Markdown to format your response.
 Code blocks must be formatted in Markdown.
-Math should be rendered with inline TeX markup, surrounded by $.
+Math should be rendered with inline TeX markup, surrounded by $. Use $ and $$ style LaTeX delimiters only.
 If you do not know the answer to a question, answer truthfully by responding that you do not know.
 The following is a friendly conversation between you and a human.
 """.strip()