docs: fix illogical wording for HASH/KEY partitioned tables and DROP PARTITION

[yahonda]

What is changed, added or deleted? (Required)

best-practices/tidb-partitioned-tables-best-practices.md said:

Although global indexes can slow down `DROP PARTITION` operations, Hash and Key partitioned tables do not support `DROP PARTITION`. Therefore, global indexes are a practical solution because these partitions are rarely truncated.

This is self-contradictory: Hash and Key partitioned tables don't support `DROP PARTITION` at all (a hard constraint), so framing it as "these partitions are rarely truncated" misstates a total lack of support as a matter of low frequency. Reworded to state that the DROP-PARTITION performance trade-off simply doesn't apply to these tables, since the operation isn't available on them.

Found while reviewing the Japanese translation of this file (which faithfully mirrored this EN wording) — flagged by a CodeRabbit review on the JA PR.

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

• 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: N/A (English wording-clarity fix)
• Other reference link(s): i18n(ja): fix mistranslations and dropped particles across the best-practices/ directory #23888 (comment) (CodeRabbit finding on the JA translation PR)

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

🤖 Generated with Claude Code

Summary by CodeRabbit

• Documentation
  • Updated partitioned-table guidance to clarify that Hash and Key partitioning do not support dropping partitions, so related global-index considerations do not apply.

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 9c5b903 and 3fe9938.

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• best-practices/tidb-partitioned-tables-best-practices.md

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📝 Walkthrough

Walkthrough

Changes

Partitioned table guidance

Layer / File(s)	Summary
Drop partition limitation best-practices/tidb-partitioned-tables-best-practices.md	The guidance states that Hash and Key partitioned tables do not support DROP PARTITION. It removes the statement that these partitions are rarely truncated.

Priority: ⬇️ Low

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

Change: Other

Merge Risk: ⚪ Minimal · up to 3fe99

The documentation accurately clarifies the supported partition operations without changing runtime behavior.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the documentation wording fix for HASH/KEY partitioned tables and DROP PARTITION. It is concise and directly reflects the main change.
Description check	✅ Passed	The description explains the wording problem, the correction, the affected file, the applicable TiDB version, the related review link, and AI involvement. The required sections are substantially compl…
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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