docs: update Markdown equation elements

[stdlib-bot]

This PR

• updates equation elements found in Markdown files

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/log10f	$\\color{green}288/288$ $\\color{green}+100.00\\%$	$\\color{green}16/16$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}288/288$ $\\color{green}+100.00\\%$
math/base/special/sechf	$\\color{green}170/170$ $\\color{green}+100.00\\%$	$\\color{green}5/5$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}170/170$ $\\color{green}+100.00\\%$
number/int64/base/identity	$\\color{green}189/189$ $\\color{green}+100.00\\%$	$\\color{green}5/5$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}189/189$ $\\color{green}+100.00\\%$
stats/base/ndarray/dnanmeanors	$\\color{green}176/176$ $\\color{green}+100.00\\%$	$\\color{green}7/7$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}176/176$ $\\color{green}+100.00\\%$
stats/base/ndarray/dnanmeanpn	$\\color{green}183/183$ $\\color{green}+100.00\\%$	$\\color{green}7/7$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}183/183$ $\\color{green}+100.00\\%$

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