Edit requests of レッドコーダーが教える、競プロ・AtCoder上達のガイドライン【中級編：目指せ水色コーダー！】

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We released Markdown parser changes on February 24, 2022. There may be some unexpected appearance changes in this update, because this article was posted before the changes.
Please don't forget to check the preview before updating your article.
For more information on the changes, please read this article.