pivot_longer() runs the same code for column selection twice

[mikemahoney218]

Hi folks!

I believe the pivot_longer() section here should be using : to select columns, rather than -plot_id:

R-ecology-lesson/03-dplyr.Rmd

Lines 601 to 608 in 8e955fe

	In pivoting longer, we also need to specify what columns to reshape. If the columns are directly adjacent as they are here, we don't even need to list the all out: we can just use the `:` operator!
	```{r, purl=FALSE}
	surveys_long <- surveys_wide %>%
	pivot_longer(names_to = "genus", values_to = "mean_weight", cols = -plot_id)
	str(surveys_long)
	```

Later in the lesson, the text says "we could have also used -", which makes me think this is an accident of copy and paste and the former should have used ::

R-ecology-lesson/03-dplyr.Rmd

Lines 616 to 624 in 8e955fe

	We could also have used a specification for what columns to exclude. In this example,
	we will use all columns _except_ `plot_id` for the names variable. By using the minus sign in the `cols` argument,
	we omit `plot_id` from being reshaped
	```{r, purl=FALSE}
	surveys_wide %>%
	pivot_longer(names_to = "genus", values_to = "mean_weight", cols = -plot_id) %>%
	head()
	```

Happy to contribute a PR if this is unintentional.