update for 18.0 - part 6

[koizumistr]

以下のファイルの 18.0 対応です。

• ref/insert.sgml
• ref/update.sgml

[Copilot]

Pull Request Overview

This PR updates the Japanese documentation for PostgreSQL 18.0, specifically improving the translations in the INSERT and UPDATE SQL command reference pages. The changes replace machine-translated Japanese text with more natural, human-readable Japanese translations.

Key changes:

• Improved RETURNING clause documentation with clearer explanations of OLD/NEW row references
• Enhanced descriptions of output_alias parameters and their usage
• Refined example descriptions for better clarity

Reviewed Changes

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

File	Description
doc/src/sgml/ref/update.sgml	Improved Japanese translations for UPDATE command documentation, including RETURNING clause descriptions, OLD/NEW row alias explanations, and example descriptions
doc/src/sgml/ref/insert.sgml	Improved Japanese translations for INSERT command documentation, with parallel improvements to RETURNING clause and OLD/NEW row handling descriptions

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[noborus]

確認しました。