[Doc] Add example for setting multiple variables (backport #35940)

[mergify]

This is an automatic backport of pull request #35940 done by Mergify.
Cherry-pick of 8718b9d has failed:

On branch mergify/bp/branch-2.5/pr-35940
Your branch is up to date with 'origin/branch-2.5'.

You are currently cherry-picking commit 8718b9d308.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   docs/zh/sql-reference/sql-statements/Administration/SET.md

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   docs/en/sql-reference/sql-statements/Administration/SET.md

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[mergify]

@mergify[bot]: Backport conflict, please reslove the conflict and resubmit the pr

[github-actions]

[FE Incremental Coverage Report]

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[github-actions]

[BE Incremental Coverage Report]

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