docs: fix sync-diff-inspector limitations in migration tools (#23887) (#23903)

[ti-chi-bot]

This is an automated cherry-pick of #23903

This is an automated cherry-pick of #23887

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.

Which TiDB version(s) do your changes apply to? (Required)

Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions.

• 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)
• v6.1 (TiDB 6.1 versions)
• v5.4 (TiDB 5.4 versions)
• v5.3 (TiDB 5.3 versions)

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

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

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

• Documentation
  • Clarified sync-diff-inspector limitations for online data migration checks between MySQL and TiDB.
  • Clarified limitations when comparing certain data types and repairing inconsistent data in tables without a primary key or unique index.

[ti-chi-bot]

@ti-chi-bot This PR has conflicts, I have hold it.
Please resolve them or ask others to resolve them, then comment /unhold to remove the hold label.

[ti-chi-bot]

@ti-chi-bot: ## If you want to know how to resolve it, please read the guide in TiDB Dev Guide.

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📝 Walkthrough

Walkthrough

The sync-diff-inspector limitation bullet in the migration tools documentation was reworded to state its online-check and data-repair limitations more precisely.

Changes

Migration tools documentation

Layer / File(s)	Summary
Sync-diff-inspector limitation text migration-tools.md	The limitation bullet now states that online checks for MySQL-to-TiDB migration are unsupported. It also describes limitations for comparing certain data types and repairing inconsistent data in tables without a primary key or unique index.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~2 minutes

Change: Other

Suggested reviewers: qiancai

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the documentation change to sync-diff-inspector limitations in the migration tools overview. The issue references add noise but do not obscure the main change.
Description check	✅ Passed	The description explains the documentation change, identifies the affected TiDB version, and provides related PR and reference links. It omits the optional first-time contributor and AI-agent sections…
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.

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[qiancai]

/approve

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