update from density to pmf

[ScoobyP]

This will fix the typo of 'density' to 'mass function (PMF)', in the formula of binomial distribution.
As the binomial distribution has discrete random variables, its distribution is always a Probability Mass Function (PMF) and not Probability Density Function (PDF)

[ScoobyP]

Hello,

I came across this page while learning about binomial distribution for a math concept required in machine learning. Since this is my first pull request, I want to express my gratitude for the opportunity to contribute. I apologize if I’ve made any mistakes in the process or in the order of performing the pull request. I appreciate your understanding and any feedback you may have.

Thank you!

[WarrenWeckesser]

Thanks for your interest in improving NumPy!

This is not the correct repository for making the suggested change. This repository is generated from the source code at https://github.com/numpy/numpy. You'll have to create a new pull request over there to fix this documentation. Specifically, the places to be changed are

https://github.com/numpy/numpy/blob/9e43697124aa7b854f6515b189233286f6a305d7/numpy/random/_generator.pyx#L3013

and, for the legacy interface,

https://github.com/numpy/numpy/blob/9e43697124aa7b854f6515b189233286f6a305d7/numpy/random/mtrand.pyx#L3419