remove dplyr from vignette

Author: jhelvy

vignettes/design.Rmd

@@ -28,7 +28,6 @@ Before starting, let's define some basic profiles and priors to work with:
 
 ```{r}
 library(cbcTools)
-library(dplyr)
 
 profiles <- cbc_profiles(
   price = c(1, 1.5, 2, 2.5, 3),