[SPARK-20490][SPARKR][DOC] add family tag for not function

## What changes were proposed in this pull request?

doc only

## How was this patch tested?

manual

Author: Felix Cheung <felixcheung_m@hotmail.com>

Closes #17828 from felixcheung/rnotfamily.

R/pkg/R/functions.R

@@ -3871,6 +3871,7 @@ setMethod("posexplode_outer",
 #' @rdname not
 #' @name not
 #' @aliases not,Column-method
+#' @family normal_funcs
 #' @export
 #' @examples \dontrun{
 #' df <- createDataFrame(data.frame(