broken link to Shiny cheatsheet

[amantaya]

Link to Shiny cheatsheet seems to be broken. 404 error.

mastering-shiny/basic-app.Rmd

Line 250 in 718db20

Now is a great time to grab a copy of the [Shiny cheatsheet](https://github.com/rstudio/cheatsheets/raw/master/shiny.pdf).

[evgeny-vlasov]

Another broken link in line 329:
- You can make your own functions to generate Bootstrap components that Shiny doesn't provide, as explained in "[Utility classes](https://rstudio.github.io/bslib/articles/theming.html#utility-classes)".

[nav9]

I came here to report the cheatsheet broken link. Howcome nobody resolved this issue yet?