[Rd] Small typo in Sweave.Rnw

[Enrico Schumann]

In the first paragraph of Sweave.Rnw
(./src/library/utils/vignettes/Sweave.Rnw), it reads

  for literate programming \cite{fla:Knuth:1984}.

but probably should be

  for literate programming \citep{fla:Knuth:1984}.
                                ^

kind regards
    Enrico
    
-- 
Enrico Schumann
Lucerne, Switzerland
http://enricoschumann.net