chore: Convert emphasis to proper heading (#2346)

Author: KATO-Hiro

docs/dev-notes/2025-10-26/impact-analysis/report.md

@@ -751,7 +751,7 @@ export function createContestTaskPairKey(contestId: string, taskId: string): Con
 
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-**レポート終了**
+## レポート終了
 
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