Fixes a small typo in docstring for scale_linewidth (#6331)

* Update scale-linewidth.R

fixes a small typo

* document

---------

Co-authored-by: Teun van den Brand <[email protected]>

Author: rdboyes

R/scale-linewidth.R

@@ -2,7 +2,7 @@
 #'
 #' `scale_linewidth` scales the width of lines and polygon strokes. Due to
 #' historical reasons, it is also possible to control this with the `size`
-#' aesthetic, but using `linewidth` is encourage to clearly differentiate area
+#' aesthetic, but using `linewidth` is encouraged to clearly differentiate area
 #' aesthetics from stroke width aesthetics.
 #'
 #' @name scale_linewidth