audit for backticked package names

[simonpcouch]

In many places in rsample, the package name is written "rsample" rather than "rsample" (i.e. there are backticks before and after the package name). Per tidy style, package names don't need backticks.

Here's an example GitHub search:

https://github.com/search?q=repo%3Atidymodels%2Frsample%20%22%60rsample%60%22&type=code

Let's search for tidymodels and tidyverse package names and make sure they're not backticked.

The part that makes this a little more tricky than a Find and Replace is knowing when the thing should actually be backticked vs. not. If the text is definitely referencing rsample as a package, take the backticks away. If there's e.g. a reference to the tune() function rather than the package tune, leave it as is (making sure to include parentheses following function names if needed). Be sure to devtools::document() and/or devtools::build_readme() if needed before putting in the PR!