system-variables: fix a typo for "GROUP" (#14198)

[ti-chi-bot]

This is an automated cherry-pick of #14198

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

• This PR is translated from: system-variables: fix a typo for "GROUP" docs-cn#14471
• Other reference link(s):

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• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

[qiancai]

/approve

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