Update package cheatsheet

[pitkant]

eurostat package cheatsheet that is included in RStudio's Contributed Cheatsheets page has been last updated on 2019-11-06: https://rstudio.github.io/cheatsheets/eurostat.pdf

We should check its contents, see if all examples still work and update if necessary.

https://github.com/rOpenGov/eurostat/tree/master/inst/extras/cheatsheet