[Rd] minor typo in duplicated.Rd (lemgth != length)

[Sean O'Riordain]

sean at sean7:~/R/RSVN/R/trunk/src/library$ svn diff
Index: base/man/duplicated.Rd
===================================================================
--- base/man/duplicated.Rd	(revision 47231)
+++ base/man/duplicated.Rd	(working copy)
@@ -64,7 +64,7 @@
   not be efficient for a very large set.
 }
 \value{
-  For a vector input, a logical vector of the same lemgth as
+  For a vector input, a logical vector of the same length as
   \code{x}.  For a data frame, a logical vector with one element for
   each row.  For a matrix or array, a logical array with the same
   dimensions and dimnames.