Remove Java11 review guidance

[ykmr1224]

Description

• Remove Java11 review guidance as we no longer backport to 2.x

Related Issues

n/a

Check List

• New functionality includes testing.
• New functionality has been documented.
• New functionality has javadoc added.
• New functionality has a user manual doc added.
• New PPL command checklist all confirmed.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff or -s.
• Public documentation issue/PR created.

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[coderabbitai]

📝 Walkthrough

Summary by CodeRabbit

• Documentation
  • Updated OpenSearch SQL guidelines to reflect the current Java requirement, removing references to Java 11 and standardizing on JDK 21.
  • Clarifies environment expectations for users and contributors following the guidelines, reducing confusion about supported Java versions.

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Walkthrough

A Java 11 compatibility guideline was removed from the OpenSearch SQL review guidelines, leaving only the JDK 21 requirement documented.

Changes

Cohort / File(s)	Summary
Review Guidelines Documentation .rules/REVIEW_GUIDELINES.md	Removed Java 11 compatibility bullet point under OpenSearch SQL guidelines section.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title succinctly describes the main change: removal of Java11 review guidance.
Description check	✅ Passed	The description directly relates to the removal of Java11 review guidance, matching the changeset.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[penghuo]

as bug fix may need to backport, I suggest we remove it when we bump to 4.x

[RyanL1997]

Should we consider adding a description of "Only security fixes or only critical bug fixes can be backported to 2.x"?