chore(docs): Format the PR references as Markdown links (#2797)

Author: KATO-Hiro

docs/dev-notes/2025-11-06/add_tests_for_contest_table_provider/plan.md

@@ -305,8 +305,8 @@ pnpm lint src/test/lib/utils/contest_table_provider.test.ts
 
 ## 8. 参考資料
 
-- PR #2286: FPS24Provider 実装（https://github.com/AtCoder-NoviSteps/AtCoderNoviSteps/pull/2286）
-- PR #2780: リファクタリング（https://github.com/AtCoder-NoviSteps/AtCoderNoviSteps/pull/2780）
+- PR #2286: FPS24Provider 実装 ([PR #2286](https://github.com/AtCoder-NoviSteps/AtCoderNoviSteps/pull/2286))
+- PR #2780: リファクタリング ([PR #2780](https://github.com/AtCoder-NoviSteps/AtCoderNoviSteps/pull/2780))
 - 参照ドキュメント: `docs/dev-notes/2025-11-01/add_and_refactoring_tests_for_contest_table_provider/plan.md`
 
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