Spelling fix in docs (#2160)

s/specifify/specify/g

Author: jdagilliland

R/scale-continuous.r

@@ -69,7 +69,7 @@ NULL
 
 #' @rdname scale_continuous
 #'
-#' @param sec.axis specifify a secondary axis
+#' @param sec.axis specify a secondary axis
 #'
 #' @seealso [sec_axis()] for how to specify secondary axes
 #' @export