remind_removing_old_cache: Ask people to remove the cache
Description
The way RStudio Startup works does not allow o read the prompt for some
reasons (https://stackoverflow.com/questions/55772436/readline-does-not-prompt-user-input-from-rprofile-site-in-rstudio)
So we better don't use the prompt and issue a message only.
Usage
remind_removing_old_cache()