docs: add memory unit example for tidb_server_memory_limit (#23587) (#23657)

[ti-chi-bot]

This is an automated cherry-pick of #23657

This is an automated cherry-pick of #23587

What is changed, added or deleted? (Required)

• Add a 90GiB example to the tidb_server_memory_limit description in system-variables.md.
• Clarify the documented unit-format example without changing the supported formats.

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

• This PR is translated from: docs: add memory unit example for tidb_server_memory_limit docs-cn#21893
• Other reference link(s): N/A

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
  • Updated the tidb_server_memory_limit and tidb_server_memory_limit_sess_min_size reference sections.
  • Revised the memory-size examples for clarity, including an updated 130MiB example.
  • No functional behavior was changed.

[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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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 242804d and 979b6f1.

📒 Files selected for processing (1)

• system-variables.md

💤 Files with no reviewable changes (1)

• system-variables.md

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📝 Walkthrough

Walkthrough

This documentation-only change revises memory-size examples in two TiDB system variable reference sections. No functional behavior changes.

Changes

Memory variable documentation

Layer / File(s)	Summary
Update memory variable reference text system-variables.md	The tidb_server_memory_limit example wording is shortened. The tidb_server_memory_limit_sess_min_size example changes from 90GiB to 130MiB.

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

Merge Risk: ⚪ Minimal · up to 979b6

This documentation-only change adds a 90GiB example for the memory limit setting without changing supported behavior. No actionable merge-blocking risk remains beyond normal checks and review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies a documentation change that adds a memory-unit example for tidb_server_memory_limit. It is concise and related to the primary change.
Description check	✅ Passed	The description includes the required change summary, affected version, and reference link sections. It omits the optional AI agent involvement section, but the required information is present.
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.

Full details: Docstring Coverage

Explanation

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 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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Actionable comments posted: 1

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ℹ️ Review info

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• system-variables.md

Included review availability: Your plan provides up to 4 included reviews per hour; 2 remain after this review.

[qiancai]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qiancai

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