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
stats/base/dists/beta/cdf	$\\color{green}337/337$ $\\color{green}+100.00\\%$	$\\color{green}29/29$ $\\color{green}+100.00\\%$	$\\color{green}4/4$ $\\color{green}+100.00\\%$	$\\color{green}337/337$ $\\color{green}+100.00\\%$
stats/base/dists/binomial/cdf	$\\color{green}343/343$ $\\color{green}+100.00\\%$	$\\color{green}33/33$ $\\color{green}+100.00\\%$	$\\color{green}4/4$ $\\color{green}+100.00\\%$	$\\color{green}343/343$ $\\color{green}+100.00\\%$
stats/base/dists/hypergeometric/kurtosis	$\\color{green}207/207$ $\\color{green}+100.00\\%$	$\\color{green}13/13$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}207/207$ $\\color{green}+100.00\\%$

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