Improve interaction between "required packages" and "our version"

[hfrick]

Currently we need to remember that packages listed in the install requirements in the intro slide decks, e.g.

workshops/slides/advanced-01-introduction.qmd

Lines 146 to 157 in ea5f289

	```{r load-pkgs}
	#| eval: false
	# Install the packages for the workshop
	pkgs <-
	c("bonsai", "Cubist", "doParallel", "earth", "embed", "finetune",
	"forested", "lightgbm", "lme4", "parallelly", "plumber", "probably",
	"ranger", "rpart", "rpart.plot", "rules", "splines2", "stacks",
	"text2vec", "textrecipes", "tidymodels", "vetiver")
	install.packages(pkgs)
	```

then also need to be included in the list of dependencies for making the "Our versions" slide:

workshops/slides/advanced-01-introduction.qmd

Lines 267 to 270 in ea5f289

	deps <-
	c("bonsai", "Cubist", "doParallel", "earth", "embed", "finetune",
	"lightgbm", "lme4", "plumber", "probably", "rules", "splines2",
	"stacks", "text2vec", "textrecipes", "tidymodels", "vetiver")

Otherwise, they don't show up on that slide because a) the list is called pkg in one and deps in the other chunk and b) the earlier code chunk never gets executed. Let's make it so that we don't have to change it manually in both places.