Link to Shiny cheatsheet at 1.7 incorrect

[wold01]

At 1.7 it says 'Now is a great time to grab a copy of the Shiny cheatsheet.' The link, however, does not link to a cheatsheet but gives an error.

The direct link should be: https://raw.githubusercontent.com/rstudio/cheatsheets/main/shiny.pdf

[olivroy]

Same as #567