Fixes # 5960 (#6036)

Changed "unscaled x" because the function takes transformed values.

Author: ccani007

R/stat-bin.R

@@ -1,8 +1,7 @@
 #' @param binwidth The width of the bins. Can be specified as a numeric value
-#'   or as a function that calculates width from unscaled x. Here, "unscaled x"
-#'   refers to the original x values in the data, before application of any
-#'   scale transformation. When specifying a function along with a grouping
-#'   structure, the function will be called once per group.
+#'   or as a function that takes x after scale transformation as input and
+#'   returns a single numeric value. When specifying a function along with a
+#'   grouping structure, the function will be called once per group.
 #'   The default is to use the number of bins in `bins`,
 #'   covering the range of the data. You should always override
 #'   this value, exploring multiple widths to find the best to illustrate the