Do not use `echo = FALSE` or `warning = FALSE` chunk options

Using `echo = FALSE` or `warning = FALSE` in tutorials means that the output online may not match what the learners are seeing on their screen when running the code.

This is a likely source of confusion and probably not a great practice IMO. If there is a warning somewhere, I would follow these steps in order of priority:

- try to reformat the code to avoid the warning, especially if it is alerting of a legitimate issue
- use the warning as a learning opportunity and explain to learners where it comes from and what it means

Additionally, if some packages are too verbose, there may be value to report the issue upstream and see if it should and can be changed there.