i18n: fix Japanese translation

[Oreoxmt]

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[gemini-code-assist]

Code Review

This pull request corrects a typo in TOC-develop.md ("MySQL Workchen" to "MySQL Workbench") and updates the translation of "Pre-GA" releases from "事前総会" to "Pre-GA" across several release documentation files (TOC-tidb-releases.md, releases/_index.md, and releases/release-timeline.md). There are no review comments, and I have no additional feedback to provide.

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-05-27 08:54:30.705598647 +0000 UTC m=+428740.675763703: ☑️ agreed by qiancai.