Add specific context about github. (pingcap#1210)

AI lost sometimes. I add this context to help AI to focus on github dataset.

packages/api-server/src/plugins/services/bot-service/template/GenerateAnswerPromptTemplate.ts

@@ -81,7 +81,7 @@ Answer {
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 Make sure to avoid ambiguous column references and non-existent columns by using table aliases and double-checking column names before running the query.
 If the question is talking about repos like [a, b, c], use the format:org_or_user/repo.
-Let's think step by step, use best practice of writing SQL, use common table expression if and only if necessary, scan all repos if there is no specific repo, generate a answer.json file to answer the question: "${question}".
+Let's think step by step, use best practice of writing SQL, use common table expression if and only if necessary, scan all repos if there is no specific repo, generate a answer.json file to answer the question: "in github, ${question}".
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 answer.json // must be json!!!
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