docs: chapter02 の誤ったコードフェンスを削除

[ootakazuhiko]

変更内容

• Chapter 02 の本文中に紛れ込んでいた ```text のコードフェンスを削除しました（docs/src 両方）。

背景

• 当該フェンスが閉じられておらず、以降の見出しや本文がコードブロックとしてレンダリングされる状態になっていました。

影響

• 表示/体裁の修正のみで、手順や主張の内容は変更しません。

[Copilot]

Pull request overview

This pull request fixes a documentation rendering issue in Chapter 02 by removing errant unclosed ```text code fence markers that were causing subsequent content to be incorrectly rendered as code blocks. The fix is applied consistently to both the src/ and docs/ versions of the chapter.

Changes:

• Removed two instances of errant ```text code fences from Chapter 02 documentation files
• Fixed markdown rendering to ensure proper display of headings and content

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/chapters/chapter02/index.md	Removed two unclosed ```text code fences (after line 57 and 89) that were breaking markdown rendering
docs/chapters/chapter02/index.md	Removed two unclosed ```text code fences (after line 66 and 98) that were breaking markdown rendering

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[ootakazuhiko]

Copilot review を確認しました。追加の指摘は無かったため、対応不要です。

• CI: docs-forbidden / qa ともに PASS を確認済み