Swap order of preserve arguments in position_dodge2() (#2545)

Author: karawoo

R/position-dodge2.r

@@ -4,7 +4,7 @@
 #'   shrunk by this proportion to allow space between them. Defaults to 0.1.
 #' @param reverse If `TRUE`, will reverse the default stacking order.
 #'   This is useful if you're rotating both the plot and legend.
-position_dodge2 <- function(width = NULL, preserve = c("single", "total"),
+position_dodge2 <- function(width = NULL, preserve = c("total", "single"),
                             padding = 0.1, reverse = FALSE) {
   ggproto(NULL, PositionDodge2,
     width = width,