[Rd] Wrong explanation on 'ylab' in hist.Rd

[Martin Maechler]

>>>>> suharto anggono--- via R-devel 
>>>>>     on Sun, 6 Oct 2019 12:14:23 +0000 writes:

    > Description of arguments main, xlab, ylab in hist.Rd in current R devel and R patched ends with this.
    > the default \code{ylab} is \code{"Frequency"} iff \code{probability} is true

    > In fact, if 'probability' is true, the histogram doesn't represent frequencies.

    > It should be
    > the default \code{ylab} is \code{"Frequency"} iff \code{freq} is true

yes, of course. <.. blush ..>