Fix PR#18857. By Arni Magnusson.

git-svn-id: https://svn.r-project.org/R/trunk@87716 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: hornik

doc/THANKS

@@ -23,7 +23,7 @@ Others have written code that has been adopted by R and is
 acknowledged in the code files, including
 
 J. D. Beasley, David J. Best, Richard Brent, Kevin Buhr, Michael
-A. Covington, Bill Cleveland, Robert Cleveland,, G. W. Cran,
+A. Covington, Bill Cleveland, Robert Cleveland, G. W. Cran,
 C. G. Ding, Ulrich Drepper, Paul Eggert, J. O. Evans, David M. Gay,
 H. Frick, G. W. Hill, Richard H. Jones, Eric Grosse, Shelby Haberman,
 Bruno Haible, John Hartigan, Andrew Harvey, Trevor Hastie, Min Long