fix: correct doctest expected value in read-dir examples (issue #13252)

[NotFoundOvO]

resolves #13252

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Coverage Report

Package	Statements	Branches	Functions	Lines
fs/read-dir	$\\color{green}171/171$ $\\color{green}+100.00\\%$	$\\color{green}7/7$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}171/171$ $\\color{green}+100.00\\%$

The above coverage report was generated for the changes in this PR.