Missing an actual code example for the concept that "'Outdated' does not always mean 'will be run'"

[joelnitta]

The current lesson describes this in words:

targets-workshop/episodes/lifecycle.Rmd

Lines 192 to 202 in b471c64

	Just because a target appears as light blue (is "outdated") in the network visualization, this does not guarantee that it will be re-built during the next run. Rather, it means that **at least of one the targets that it depends on has changed**.
	For example, if the workflow state looked like this:
	`A -> B* -> C -> D`
	where the `*` indicates that `B` has changed compared to the last time the workflow was run, the network visualization will show `B`, `C`, and `D` all as light blue.
	But if re-running the workflow results in the exact same value for `C` as before, `D` will not be re-run (will be "skipped").
	Most of the time, a single change will cascade to the rest of the downstream targets and cause them to be re-built, but this is not always the case. `targets` has no way of knowing ahead of time what the actual output will be, so it cannot provide a network visualization that completely predicts the future!

but we could actually do live coding to demonstrate.

for example, change the name of the target penguins_csv_file. This will invalidate everything downstream, but only that target will actually get run.