Fix duplicate items in CREATE USER and ALTER USER (#21939)

[ti-chi-bot]

This is an automated cherry-pick of #21939

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[gemini-code-assist]

Summary of Changes

Hello @ti-chi-bot, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on refining the documentation for the CREATE USER and ALTER USER SQL statements. The primary goal is to remove duplicated grammar definitions, specifically those related to REQUIRE clauses, to enhance the clarity and correctness of the official documentation.

Highlights

• Documentation Cleanup: Removed redundant grammar definitions for RequireClauseOpt and RequireList from the documentation of ALTER USER and CREATE USER SQL statements.
• Accuracy Improvement: Ensured that the documentation for user management commands is more concise and accurate by eliminating duplicate entries.

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[gemini-code-assist]

Code Review

This pull request removes duplicate EBNF definitions for RequireClauseOpt and RequireList from the documentation for the ALTER USER and CREATE USER statements. These changes correctly eliminate redundancy and improve the clarity and maintainability of the documentation. The changes are accurate and I have no further suggestions.