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/anglit/skewness	$\\color{green}175/175$ $\\color{green}+100.00\\%$	$\\color{green}9/9$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}175/175$ $\\color{green}+100.00\\%$
stats/base/dists/burr-type3/cdf	$\\color{green}316/316$ $\\color{green}+100.00\\%$	$\\color{green}25/25$ $\\color{green}+100.00\\%$	$\\color{green}4/4$ $\\color{green}+100.00\\%$	$\\color{green}316/316$ $\\color{green}+100.00\\%$
stats/base/dists/log-logistic/variance	$\\color{green}200/200$ $\\color{green}+100.00\\%$	$\\color{green}10/10$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}200/200$ $\\color{green}+100.00\\%$
stats/base/dists/wald/cdf	$\\color{green}361/361$ $\\color{green}+100.00\\%$	$\\color{green}35/35$ $\\color{green}+100.00\\%$	$\\color{green}4/4$ $\\color{green}+100.00\\%$	$\\color{green}361/361$ $\\color{green}+100.00\\%$

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