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/pdf	$\\color{green}319/319$ $\\color{green}+100.00\\%$	$\\color{green}25/25$ $\\color{green}+100.00\\%$	$\\color{green}4/4$ $\\color{green}+100.00\\%$	$\\color{green}319/319$ $\\color{green}+100.00\\%$
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/logpmf	$\\color{green}363/363$ $\\color{green}+100.00\\%$	$\\color{green}46/46$ $\\color{green}+100.00\\%$	$\\color{green}4/4$ $\\color{green}+100.00\\%$	$\\color{green}363/363$ $\\color{green}+100.00\\%$
stats/base/dists/binomial/quantile	$\\color{red}522/524$ $\\color{green}+99.62\\%$	$\\color{red}61/62$ $\\color{green}+98.39\\%$	$\\color{green}6/6$ $\\color{green}+100.00\\%$	$\\color{red}522/524$ $\\color{green}+99.62\\%$
stats/incr/nansumprod	$\\color{green}135/135$ $\\color{green}+100.00\\%$	$\\color{green}8/8$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}135/135$ $\\color{green}+100.00\\%$

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