Get rid of the RStudio symbol set

[gaborcsardi]

It causes issues: tidyverse/tidyverse#256

We'll just use ASCII on Windows, in RStudio as well. And get rid of the Windows symbol set as well.

[light2802]

I would like to contribute to this issue.

[dpprdan]

Possibly make this dependent on UTF-8 support (UCRT in R 4.2+)?