docs: fix sync-diff-inspector limitations in migration tools (#21937)

[ti-chi-bot]

This is an automated cherry-pick of #21937

What is changed, added or deleted? (Required)

This PR updates the sync-diff-inspector row in migration-tools.md on release-8.5 to match the detailed stable documentation.

• Remove the incorrect statement that JSON, BIT, BINARY, and BLOB data are unsupported.
• Clarify that JSON, BLOB/VARBINARY, and BIT are supported.
• Point readers to the detailed restrictions page for FLOAT/DOUBLE and collation-related considerations.

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• master (the latest development version)
• v8.5 (TiDB 8.5 versions)
• v8.4 (TiDB 8.4 versions)
• v8.3 (TiDB 8.3 versions)
• v8.2 (TiDB 8.2 versions)
• v8.1 (TiDB 8.1 versions)
• v7.5 (TiDB 7.5 versions)
• v7.1 (TiDB 7.1 versions)
• v6.5 (TiDB 6.5 versions)

What is the related PR or file link(s)?

• This PR is translated from: docs: fix sync-diff-inspector limitations in migration tools docs#23887
• Other reference link(s):
  • sync-diff-inspector: clarify data type support and improve collation guidance docs#22165
  • https://docs.pingcap.com/zh/tidb/stable/sync-diff-inspector/sync-diff-inspector-overview/
  • https://docs.pingcap.com/zh/tidb/stable/migration-tools/

AI agent involvement

• The changes in this PR were primarily made by an AI agent on behalf of the PR author.

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

Summary by CodeRabbit

• 文档
  • 更新 sync-diff-inspector 的使用限制说明。
  • 概括在线校验、部分数据类型比较，以及无主键或唯一索引表校验与修复等场景的限制，并提供相关文档链接。

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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• migration-tools.md

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📝 Walkthrough

Walkthrough

文档将 sync-diff-inspector 的两项具体限制改为概括性说明，并链接到使用限制文档。说明覆盖在线校验、部分数据类型比较，以及无主键或唯一索引表的校验和修复。

Changes

sync-diff-inspector 文档更新

Layer / File(s)	Summary
更新使用限制说明 migration-tools.md	将原有具体限制改为概括性描述，并补充在线校验、部分数据类型比较及无主键或唯一索引表校验修复等限制场景。

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~3 minutes

Change: Other

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	标题准确概括了本次文档修复，明确指出了 sync-diff-inspector 使用限制的更新，内容简洁且与变更一致。
Description check	✅ Passed	描述包含变更内容、适用版本、关联 PR 和参考链接，并标明了 AI agent 参与情况。必需信息基本完整，且与 TiDB 8.5 的文档更新一致。
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create a new PR

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Actionable comments posted: 1

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• migration-tools.md

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[qiancai]

/approve

[ti-chi-bot]

@qiancai: You cannot manually add or delete the cherry pick approval state labels, only I and the tursted members have permission to do so. You can approve it in internal platform.

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[qiancai]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qiancai

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #21943.
But this PR has conflicts, please resolve them!