audit for backticked package names

[simonpcouch]

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

Here's an example GitHub search:

https://github.com/search?q=repo%3Atidymodels%2Fstacks%20%22%60stacks%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 stacks as a package, take the backticks away. If there's e.g. a reference to the stacks() function rather than the package stacks, leave it as is (making sure to include parentheses following function names if needed). Be sure to devtools::document() and/or devtools::build_readme() before putting in the PR!