Fix a typo caught by Gabriella Capone on docs@

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branch : 2.7
Closes #22663: patchcheck: only modify text files under Doc/

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branch : 2.7
extra : transplant_source : %3F%A5%D6%A4%BFx%82%12%3BH%D5%2BtN%01%10Q%09%BC%7D
make plural s lowercase

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branch : 2.7